1 Introduction
For an integer n\geq2, let \Pplus(n) denote its largest prime divisor, and put \Pplus(1)=1. The Dickman–de Bruijn function \rho is the continuous function on [0,\infty) determined by
The classical theory of smooth numbers, beginning with Dickman and developed by Ramaswami and de Bruijn [4, 6, 22], gives
Our result identifies the joint law at two consecutive integers.
Theorem 1.1 (Joint Dickman law). For every fixed a,b\in(0,1),
Here the limit is taken over all real X, with ordinary, unweighted counting.
Thus \log\Pplus(n)/\log n and \log\Pplus(n+1)/\log n have, in natural density, independent limiting distributions with distribution function a\mapsto\rho(1/a), continuously extended to [0,1]. Section 11 proves the corresponding law with fixed thresholds X^a,X^b, derives the displayed moving-threshold statement, and identifies this continuous limiting law. Inclusion–exclusion using the fixed-threshold law and its marginals gives the upper-tail independence conjecture of Erdős and Pomerance [7, p. 311].
The comparison conjecture usually attributed to Erdős and Turán is a consequence, rather than a separate main theorem.
Corollary 1.2. One has
The reverse ordering has the same natural density.
The limiting marginal is continuous, so its product measure gives zero mass to the diagonal; symmetry then gives the corollary. In particular, no quantitative separation estimate is needed for this deduction.
1.1 Previous work
Erdős and Pomerance [7] formulated the joint independence problem and proved that each ordering has positive lower natural density. Their explicit lower bound was 0.0099. They also proved that for every \varepsilon>0, some \delta>0 makes the number of integers n<X satisfying X^{-\delta}<\Pplus(n)/\Pplus(n+1)<X^\delta less than \varepsilon X for all sufficiently large X [7, Theorem 1]. The lower-density bound was increased to 0.05544 by de la Bretèche, Pomerance and Tenenbaum [5, Section 3], and to 0.05866 by an observation of Fouvry recorded in the same section. Wang [27, 28] obtained 0.1063 and 0.1356, and Lü and Wang [15] obtained 0.2017. Yang’s recent preprint [30, Theorem 1.4] gives 0.280 for both orderings. These are bounds on lower natural densities; they do not assert that a natural density exists.
For the joint law itself, Teräväinen [26, Theorem 1.14] proved the predicted product in logarithmic density. That is, for fixed 0<a,b<1, the indicator in Theorem 1.1, averaged with weight 1/n and normalization 1/\log X, tends to \rho(1/a)\rho(1/b). His Theorem 1.16 gives logarithmic density 1/2 for the ordering, while Theorem 1.19 proves positive lower natural density for every nondegenerate rectangle of normalized largest-prime-factor values inside (0,1)^2. Tao and Teräväinen [24, Remark 3.3, equation (50)] then obtained the joint product law for ordinary averages outside an exceptional set of scales of logarithmic density zero; their Corollary 1.16 gives the corresponding ordering result. Wang [29] proved the ordinary joint law under the Elliott–Halberstam conjecture for friable integers. Jiang, Lü and Wang [13] established averaged-over-shift forms of the conjectures, a different conclusion from a result at the fixed shift one.
The more recent work of Tao and Teräväinen [25, Theorem 1.8] gives a quantitative joint law outside an exceptional set of scales, with uniformity in the smoothness parameters and a power saving in \log X. Theorem 1.1 concerns fixed parameters and has no exceptional scales; it does not assert their quantitative error term or their uniformity for growing parameters. Relative to the results just described, the distinction is therefore the unconditional ordinary limit at every sufficiently large scale, not a new marginal distribution or a logarithmically averaged independence statement.
1.2 Method and organization
We first replace the largest prime factor by finitely many prime counts. For a fixed integer J\ge2, divide the primes in (x^{1/J},x] into bins \mathcal B_{k,x}=(x^{k/J},x^{(k+1)/J}], 1\le k<J. If \Omega_E(n) counts prime factors in E with multiplicity, a choice of unit complex numbers \zeta_k defines the bin character
Let g_x be defined by a second arbitrary phase vector, and let F_x=f_x-\mu, where \mu is the limiting mean of f_x. Finite Fourier inversion reduces the joint law to the mixed decorrelation
Here x runs through integer scales. The two phase vectors may differ. This freedom gives independence of the two count vectors.
Two properties of these functions connect the beginning and end of the proof. First, every fixed positive integer multiplier has all its prime factors below the bins once x is large. Thus F_x(un)=F_x(n) and g_x(un)=g_x(n) for each fixed u. Second, F_x has cancellation in averages over growing intervals that remain short relative to the original scale. Let B be the auxiliary parameter and let T=T(B)\to\infty be the growing shift scale. If P_B is a finite set of primes with \min P_B\to\infty, define
For any interval I_B of L_B\to\infty consecutive integer shifts, and fixed 0<s_0<s_1, positive integer D, residue r\pmod D, and v\ge0, Section 2 proves
At fixed B the shift interval is short relative to x, while the base points have size Tx. This is the scale produced by the divisor substitution below.
The centered function F_x is not multiplicative. On the relevant ranges n=O_B(x), the bin counts take values in a fixed finite set. This permits interpolation by a fixed finite family of real, nonnegative multiplicative functions. After resolving the residue condition by Dirichlet characters, the real short-interval theorem of Matomäki and Radziwiłł [16, Theorem 1] compares the principal components with long means whose centered combination vanishes. The complex theorem of Matomäki, Radziwiłł and Tao [17, Theorem A.1, corrected version] controls the nonprincipal twists. The rest of the proof must reduce the mixed correlation to this particular cancellation statement.
Suppose, then, that the mixed correlation stays nonzero along a sequence of scales. The profinite integers \widehat{\mathbb Z} encode compatible residue classes modulo all positive integers and carry Haar probability measure. Passing to a subsequence gives a bounded profile W(t,w) on (0,\infty)\times\widehat{\mathbb Z}. Its integral against each fixed compactly supported continuous test \Phi(t,w) is the subsequential limit of the mixed averages weighted by \Phi(n/x,n), with n in the second argument viewed through its residues. A fixed nonnegative compactly supported smooth cutoff \phi can be chosen so that \int\phi(t)W(t,w)\,dt\,dw\ne0, where dt is Lebesgue measure and dw is Haar measure.
For an integer n, the amplifier defines D_B(n) as a nonnegative weighted count of factorizations n=am and n+1=cl_a, restricted by e^B<c<e^{2B} and Tc<a<2Tc. At fixed B its coefficient list is finite, and the same formula defines a function on \widehat{\mathbb Z} depending only on residues at primes above a cutoff tending to infinity. The construction gives D_B Haar mean at least d_0>0 for large B and bounded L^2 norm. To prove these bounds, the argument passes to a comparison model in which each site prime is assigned by an independent fair coin to the coefficient divisor or the remaining factor. The first and second moments are analyzed through one split and two conditionally independent splits of the same site prime sets. For each fixed B, \Phi(t,w)=\phi(t)D_B(w) is an allowed profile test, so along the selected subsequence
Independence from every fixed residue coordinate and L^2 approximation of \phi W show that the right-hand side has absolute value bounded away from zero as B\to\infty.
For fixed B and large x, writing n=am in this weighted average replaces g_x(n) by g_x(m). For each fixed pair (c,m), the remaining terms form a sum over a satisfying c\mid am+1, with nonnegative divisor and smooth weights multiplying F_x(am+1). Cauchy–Schwarz in (c,m) removes the unit-modulus factor g_x(m) and squares this inner sum. The resulting normalized quadratic energy has a positive lower bound, while its equal-coefficient diagonal tends to zero in the same iterated limit. A positive contribution therefore remains from distinct indices a,b. Section 4 proves these moment and energy claims.
For such a pair, c divides both am+1 and bm+1. Thus m is a unit modulo c and a-b=jc, with 0<|j|<T by the coefficient windows. Writing l_a=(am+1)/c and l_b=(bm+1)/c, the exact substitution
turns the label product into \overline{F_x(n')}F_x(n'+j) by invariance under the fixed multipliers a,b,c. The new endpoints have size Tx. The off-diagonal energy is therefore a weighted graph of ordinary additive shifts. Its edge weights depend on endpoint prime sets and on additional residue data from each divisor representation.
Group the new endpoints into blocks N+i, 1\le i\le M, with M=\lceil C_6T\rceil for a fixed large C_6, and put s=N/(Tx). Section 5 couples the actual auxiliary-prime divisibility sets at these positions to independent model sets S_i, each formed by including every auxiliary prime p independently with probability 1/p, and averages the extra residue weight of each representation. This compares the arithmetic graph with an endpoint kernel \mathcal L_{ik}(S_i,S_k;s) in expected cut norm. Here cut norm is the largest absolute normalized pairing with two real vectors bounded by one, chosen after the matrix is known. Section 6 controls representation multiplicity and provides the averaged second-moment bounds needed for sampling.
The aim is now to replace this endpoint kernel by products of functions of its two endpoints. For an endpoint type S, let b be the product obtained by retaining each prime independently with probability 1/2. The features used in the comparison are
where the I_l form a fixed coarse partition of a compact logarithmic interval, chosen for a desired accuracy. The channel estimates in Section 7 show that fair splitting suppresses residue dependence and makes logarithmic outputs uniformly approximable on this partition. Fourier detection of a-b=jc then lets Section 8 apply arithmetic estimates to the coefficient c and these channel estimates to the endpoints. The resulting comparison has the form
where i,k are the endpoint positions. The scalar coefficients separate an arithmetic factor in |j| from a smooth factor in the normalized lag |j|/T and the common block origin s. The number of features is fixed, while their values and the coefficients may depend on B.
The feature comparison first holds after integration against separate functions of the two independent endpoint sets. The actual labels need not have this single-site form, and an optimizing test can depend on the whole configuration. Section 9 upgrades the comparison to expected cut norm by approximating an optimizing cut with a small sample of columns. Finally, polynomial approximation of each log-window indicator expresses V_l, up to a small mean-square error, as a fixed finite combination of
At an integer endpoint these are exactly G_{B,v}. The arithmetic lag factor is approximated in mean over lags by a fixed periodic function. For a fixed small \delta>0 chosen for the desired accuracy, subdivide each position block into a fixed number of intervals whose lengths grow with T and are at most \delta T. Within each interval pair, the normalized lag varies by at most 2\delta. Approximating the smooth lag factor there and resolving the periodic factor into fixed residue classes turns the feature energy, up to a controlled error, into products of the weighted short averages already controlled in Section 2. Their vanishing contradicts the positive energy. Sections 10 and 11 complete this argument and the passage from bin events to the joint law.
The divisor amplification and graph comparison have close antecedents in Tao’s logarithmic correlation argument [23], the prime-divisibility graphs of Helfgott and Radziwiłł [12], Pilatte’s product-of-primes amplification [21], and the mixed-function decoupling of Tao and Teräväinen [25, Section 3.1]. The present rough-divisor graph and its endpoint comparison are proved locally. The sampling argument likewise builds on the cut-based methods of Frieze and Kannan [10], Alon, Fernandez de la Vega, Kannan and Karpinski [1, Lemma 3], and Borgs, Chayes, Lovász, Sós and Vesztergombi [2, Theorem 4.6]. Because the kernels here vary with B and can be large, the proof establishes the moment bounds needed before applying bounded-differences concentration [18].
The arithmetic estimates are developed in Section 3 using Selberg–Delange theory, character estimates and upper-bound sieves in the forms recorded by Granville and Koukoulopoulos [11], Koukoulopoulos [14], and Ford [8, 9]. The minor-arc input in Section 8 is the exponential-sum estimate of Montgomery and Vaughan [20]. Throughout the proof, the original scale x tends to infinity before the auxiliary scale B. Bin data, feature degrees, residue moduli and divisor multipliers are fixed in that inner limit. The contradiction applies to a subsequence of every possible bad sequence of original scales, and hence yields the full ordinary limit.
2 Large-prime labels and their short averages
We encode the large prime factors by two independently chosen multiplicative labels. Their one-variable distributions have limits independent of fixed residue conditions. We establish those limits and the weighted short-average estimate needed to prove that the two labels decorrelate at consecutive integers. In the short-average estimate the original counting scale x tends to infinity before the auxiliary parameter B does. The scale x>1 is real unless a statement explicitly restricts it to integers.
2.1 Labels and their one-variable distributions
Fix an integer J\geq2. For 1\leq k<J put
If E is a set of primes, \Omega_E(n) denotes the number of prime factors of n belonging to E, counted with multiplicity. Fix complex numbers \zeta_1,\ldots,\zeta_{J-1} and \xi_1,\ldots,\xi_{J-1} of absolute value one, independent of x, with no relation required between the two vectors. Define the completely multiplicative function f_x by
Define the completely multiplicative label associated with (\xi_k) by
Both labels have absolute value one. For every fixed C>0, every integer n\leq Cx has at most J prime factors in the union of the bins, once x is sufficiently large in terms of C,J. Indeed, J+1 such factors would have product exceeding x^{1+1/J}>Cx.
Lemma 2.1 (One-variable distribution). For every fixed 0<\alpha<\beta<\infty, positive integer q, and residue class a\pmod q, the distribution of
among the integers \alpha x<n\leq\beta x, n\equiv a\pmod q, normalized to have mass one, converges as x\to\infty. Its limit depends only on J, and not on \alpha,\beta,q,a.
Consequently there is a number \mu=\mu(J,\zeta_1,\ldots,\zeta_{J-1}) with |\mu|\leq1 such that
The same assertion holds for g_x, with a mean \mu_g depending only on J and the vector (\xi_k)_{k=1}^{J-1}. Write
Then |F_x(n)|\leq2, and for every fixed positive integer u,
for all sufficiently large x in terms of u,J.
Proof. We prove convergence by computing all mixed factorial moments of the bin counts. We first record the elementary prime estimates used in this calculation. Put \vartheta(z)=\sum_{p\le z}\log p. For z\ge2 we have
Indeed, the primes in (m,2m] divide \binom{2m}{m}, giving \vartheta(2m)-\vartheta(m)\ll m. Dyadic summation proves the first estimate, and separating the primes at \sqrt z proves the second. Moreover,
because the terms with \nu\ge2 are O(\sqrt z\log z). Expanding \log n over prime powers now gives
The floor errors use the preceding prime-power bound, and the terms with \nu\ge2 use \sum_p\sum_{\nu\ge2}(\log p)/p^\nu<\infty. Integral comparison on the left proves the third estimate in (2.7). Partial summation yields
as well as \sum_{p\le z}1/p=\log\log z+O(1).
The number of integers n\leq\beta x divisible by p^2 for some prime p>x^{1/J} is at most
This remains negligible relative to the size of any one fixed progression in the lemma. We may therefore replace multiplicity counts by counts of distinct primes.
For the mixed factorial moments of these distinct-prime counts, write (b)_r=b(b-1)\cdots(b-r+1) and (b)_0=1. Fix nonnegative integers r_1,\ldots,r_{J-1}, and let r=r_1+\cdots+r_{J-1}. The case r=0 is immediate. For r>0, a term in the factorial-moment expansion selects, in order, r_k distinct primes from bin k, for each k. Denote their product by d; only d\leq\beta x can contribute. The number of such selections is O_{J,\beta,r}(x/\log x). To see this, fix every selected prime except one, and write d_1 for their product. If the last prime has any admissible choice, its upper bound \beta x/d_1 exceeds x^{1/J}. The prime-counting upper bound therefore gives at most
choices. Summing this bound over the other primes costs a bounded product of reciprocal prime sums over the bins. We may drop distinctness and product restrictions when taking this upper bound.
For sufficiently large x, every selected prime is coprime to q. The Chinese remainder theorem then gives
The sum of the errors over all selections is o(x). After normalization, the factorial moment is consequently the reciprocal sum over the selections with d\leq\beta x, up to o(1).
In the variable v=\log p/\log x, (2.8) says that the reciprocal prime measure on bin k converges to dv/v on (k/J,(k+1)/J]. The product restriction is
The limiting product measure is absolutely continuous, so the boundary \sum v=1 has measure zero. Repeated selections do not change the limit: their reciprocal contribution is bounded by a constant times \sum_{p>x^{1/J}}p^{-2}=o(1). Returning from distinct-prime counts to multiplicity counts also costs o(1) in the normalized moment, because the exceptional set has size o(x) and the counts are bounded.
List the selected bin indices as k_1,\ldots,k_r, with r_k occurrences of k. We have proved the explicit limit
For r=0, both sides are one. The right-hand side depends only on J and the multi-index (r_k). All count vectors lie in a fixed finite set, and mixed factorial polynomials span the functions on that set. The asserted distributional convergence follows.
Taking the expectation of the function (b_k)\mapsto\prod_k\zeta_k^{b_k} gives (2.4); using the vector (\xi_k) gives the mean \mu_g. Finally, if every prime factor of u is at most x^{1/J}, then f_x(u)=g_x(u)=1. Complete multiplicativity of f_x and g_x proves (2.6).
The centered function F_x is not asserted to be multiplicative. Its eventual invariance under each fixed multiplier is the exact property in (2.6) that will be used below.
The same distributional limit holds for averages over 1\leq n\leq x. Indeed, apply the lemma to any fixed function of the count vector on \alpha x<n\leq x, then let \alpha\downarrow0; that function is bounded on the finite set of possible vectors, so the omitted interval has normalized contribution O(\alpha). In particular, the limit in (2.9) is unchanged when its normalized progression sum is replaced by x^{-1}\sum_{1\le n\le x}\prod_k(\Omega_{\mathcal B_{k,x}}(n))_{r_k}. This gives (2.4) on the initial segment as well. A fixed shift of the integer argument changes only a bounded number of terms after nonpositive arguments are omitted, so the label means have the same limits after such a shift.
2.2 The mixed correlation and its short-average input
The joint law will follow by finite Fourier inversion from the following statement for the two independently chosen phase vectors. The factor F_x(n+1) is centered, while g_x(n) has absolute value one.
Proposition 2.2 (Mixed decorrelation). For every fixed integer J\geq2 and every pair of fixed phase vectors (\zeta_k)_{k=1}^{J-1} and (\xi_k)_{k=1}^{J-1} of absolute value one, the corresponding labels satisfy
where F_x=f_x-\mu and the limit is through all integer scales.
After establishing the short-average input below, we will suppose that the average in (2.10) stays a fixed positive distance from zero along a sequence and derive a contradiction. The input is used in Section 10 at the final step of the proof.
For each auxiliary parameter B, let P_B be a finite set of primes, and suppose that \min P_B\to\infty as B\to\infty. An empty set may be allowed by interpreting its minimum as +\infty and its product as one. For a fixed real v\geq0, define
This is a real, nonnegative, 1-bounded multiplicative function. For fixed B it is periodic, with period dividing \prod_{p\in P_B}p. To see its fair-split meaning, put S_B(m)=\{p\in P_B:p\mid m\} and form a random product b by including each prime of S_B(m) independently with probability 1/2. The empty product is one. Independence gives
These are the fair-split averages used to approximate the endpoint features in Section 10.
Lemma 2.3 (Weighted short averages of the centered labels). Let T=T(B)\to\infty, let L_B be positive integers tending to infinity, and let a_B be any integer for each B. Fix 0<s_0<s_1<\infty, a positive integer D, a residue r\pmod D, and v\geq0. Then
For each fixed B all the arguments of the arithmetic functions are positive once x is sufficiently large. The same conclusion holds if the inner upper limit is taken along any sequence x\to\infty.
The proof interpolates the centered function of the finitely many bin counts by real, nonnegative multiplicative functions. Once the residue of the origin n is fixed, the congruence on i becomes a fixed residue condition on the argument m=n+i. Resolving that condition by Dirichlet characters produces two different tasks. For the principal character, short averages must be compared with long means whose centered linear combination vanishes. For a nonprincipal character, the short averages themselves must be small. We record the two published inputs for these tasks and prove the required distance estimate before returning to the weighted lemma.
2.3 The short-interval inputs
For a bounded arithmetic function g and H>0, set
For a 1-bounded multiplicative function g, define
We use the following two forms of the short-interval theorems. Their uniformity in the multiplicative function is part of the statements.
Theorem 2.4 (Real short-interval comparison). There is a function r(H) tending to zero as H\to\infty such that, for every real multiplicative function g:\N\to[-1,1] and 2\leq H\leq X,
This is a consequence of the uniform exceptional-set estimate in [16, Theorem 1], using boundedness to pass to mean square. The terms in that estimate depending on X can be absorbed into r(H) because X\geq H.
Theorem 2.5 (Complex short averages). For every multiplicative function g:\N\to\C with |g|\leq1 and X\geq H\geq10,
with an absolute implied constant.
This is [17, Theorem A.1], in the revised version with the corrected proof of Proposition A.3. That proof permits the factor e^{-M}; we use the weaker (1+M)e^{-M}, which also covers M<1. Thus divergence of the minimum over |t|\leq X suffices for our application.
The preceding statements also hold with integer origins, at the cost of an error tending to zero with H. Indeed, for |g|\leq1,
Integrating over unit intervals proves the claim, with O(1/X) errors at the endpoints. Changing a short interval endpoint by a bounded amount similarly costs O(1/H).
2.4 A uniform estimate for the character twists
Lemma 2.6 (Fixed nonprincipal characters). Fix J\geq2, positive constants c,C, a nonprincipal Dirichlet character \chi of modulus q_\chi, and a finite set E of primes. Suppose that, for each x, h_x is a 1-bounded multiplicative function satisfying
With X=cx, one has
The assertion is uniform over all the functions h_x with this prime agreement. The threshold for x may depend on J,c,C,\chi,E.
Proof. Put y=x^{1/J} and \sigma=1+1/\log x. For large x we have y<X. Since the summands defining the distance are nonnegative, we can restrict to p\leq y and delete E and the primes dividing the modulus of \chi. Deleting those finitely many primes costs only a constant in the lower bounds below.
We record a prime-sum comparison, uniform in any factors of absolute value at most one. Replacing the weight 1/p on p\leq y by p^{-\sigma} on all primes has absolute error O_J(1). Below y, the error is at most
For the tail, partial summation and the prime-counting bound in (2.7) give
The prime-power terms in the logarithm of either a zeta or a Dirichlet L Euler product are also uniformly O(1) for \sigma>1.
For |t|\leq1 it follows that
Here we used only an upper bound for the logarithm: a nonprincipal Dirichlet L-function has no pole at 1 and is bounded on the compact region under consideration. Since (2.8) and the accompanying partial-summation estimate give \sum_{p\leq y}1/p=\log\log x+O_J(1), this proves a lower bound \log\log x-O_{J,\chi,E}(1) for this frequency range.
For |t|>1, let m be the order of \chi on the units. The elementary inequality |1-z^m|\leq m|1-z|, for |z|=1, gives
The Vinogradov–Korobov bound, with any fixed logarithmic exponent strictly between 2/3 and 1, gives
The bound on the line 1 follows from [8, (1.2)]. Its extension to the right can be seen by applying the Phragmén–Lindelöf principle in 1\leq\sigma\leq2 to
The pole at 1 is removed, the logarithmic power has an analytic branch in this strip, and both vertical boundaries are bounded. For |\operatorname{Im}s|\geq1, the removed rational factor is bounded away from zero, which gives (2.17). For \sigma\geq2 the same estimate follows from absolute convergence. Applying the prime-sum comparison just proved, we obtain uniformly for 1<|t|\leq CX,
Combining the two frequency ranges proves
which implies (2.16).
2.5 Proof of the weighted short-average lemma
Proof of Lemma 2.3. Teräväinen [26, Section 4, proof of Theorem 1.11] uses real multiplicative generating functions for large-prime counts and recovers event coefficients from them. Here the finite count range gives a pointwise tensor interpolation of the centered function of all bin counts by completely multiplicative functions. We prove this interpolation with coefficients independent of B,x. Choose J+1 distinct numbers in (0,1]. The Vandermonde matrix whose entries are their powers of orders 0,\ldots,J is invertible. Taking tensor products over the J-1 count coordinates shows that there are finitely many complex constants c_\ell and vectors \boldsymbol z_\ell=(z_{\ell,1},\ldots,z_{\ell,J-1})\in(0,1]^{J-1} such that
The coefficients and vectors depend only on the fixed labels and J. Define
Each h_{\ell,x} is real, nonnegative, 1-bounded, and completely multiplicative. On every interval m\leq C_Bx with C_B fixed for fixed B, the identity F_x(m)=\sum_\ell c_\ell h_{\ell,x}(m) holds for all sufficiently large x.
We next prove the needed estimate for each fixed residue class of the integer argument. For a class r'\pmod D, put d=\gcd(r',D) and q=D/d, and write m=dk. Then m\equiv r'\pmod D is equivalent to k\equiv r'/d\pmod q, a unit class modulo q. For all sufficiently large B, no prime factor of d belongs to P_B, so G_{B,v}(dk)=G_{B,v}(k). For fixed B and sufficiently large x, (2.6) also gives F_x(dk)=F_x(k), and the same equality holds for every interpolant h_{\ell,x}.
By character orthogonality, the restricted k-sum is a fixed linear combination of sums of
All these functions are 1-bounded and multiplicative. The sum length after division by d is H_B=L_B/d. Normalization by L_B is d^{-1} times normalization by H_B. Changing integer endpoints introduces an error O_D(L_B^{-1}).
Consider first the principal character \chi_0\pmod q. The functions in (2.19) are then real, so Theorem 2.4 applies to each interpolant. Although their individual long means need not vanish, their centered linear combination does. More precisely, on any dyadic interval [X,2X] with X=c_Bx and c_B>0 fixed for fixed B,
To justify the last limit, split the sum into residue classes modulo the fixed common period of G_{B,v} and \chi_0, and apply Lemma 2.1 to every class. The number and the sizes of these residue classes may depend on B; they are fixed in this x-limit. The mean square of the centered short average thus has inner upper limit at most a fixed multiple of r(H_B), where the multiple depends on the interpolation coefficients and D, but not on B.
For a nonprincipal \chi, the function in (2.19) equals \chi(p) at all primes p\leq x^{1/J} outside the finite set P_B. Lemma 2.6 therefore applies for each fixed B, with X=c_Bx and the frequency range |t|\leq X. For all sufficiently large B we have H_B\geq10, so Theorem 2.5 applies once x is sufficiently large. Taking the inner upper limit in (2.15) leaves at most a constant times (\log\log H_B/\log H_B)^2. This tends to zero as B\to\infty. There are only finitely many interpolants and characters, so the same holds after their linear combination.
Finally, for a given origin n, the condition i\equiv r\pmod D in (2.12) is the condition m=n+i\equiv n+r\pmod D. There are only D possible argument residues r', and it suffices to sum the bounds just proved for these possibilities. After m=dk, the short-interval origin is (n+a_B)/d. For fixed B and all sufficiently large x,
Choose a dyadic cover of the fixed scaled interval [s_0T/(2d),2s_1T/d]. It gives intervals [c_{B,j}x,2c_{B,j}x] with every c_{B,j}>0 fixed in the inner x-limit, and with a number of intervals bounded in terms of s_0,s_1,D independently of B. Their scales are comparable to Tx/d. Mapping the origins to their integer parts has multiplicity at most d+1, and replacing an origin by its integer part costs O(H_B^{-1}). The integer-origin version of the preceding estimates consequently applies. Normalizing by Tx instead of the length of each dyadic range changes only fixed factors. Since H_B=L_B/d\to\infty for every d\mid D, this proves (2.12).
All assertions used an unrestricted upper limit as x\to\infty; restricting that upper limit to a subsequence preserves them.
2.6 A profile of a nonzero mixed correlation
We begin the proof by supposing that Proposition 2.2 fails. Fix an offending J and pair of phase vectors. Boundedness permits passing to a subsequence on which the mixed correlation has a nonzero limit:
The arithmetic amplification in the following sections will contradict this limit; Section 10 completes the argument.
Let \whZ be the profinite integers, with Haar probability measure dw, and identify every integer with its natural image in \whZ. On (0,\infty)\times\whZ define the locally finite measures
Unweighted scale counting gives \lambda_x\to dt\,dw against compactly supported continuous tests. This follows first for a continuous test in t times a residue-class indicator in w by progression counting, and then for every compactly supported continuous test by uniform approximation. Also |\nu_x|\le2\lambda_x. The resulting uniform variation bounds on compact sets, weak compactness on a countable exhaustion, and a diagonal extraction give a further subsequence along which \nu_x converges against these tests to a locally finite complex measure \nu.
For every compactly supported continuous \Phi, the weak convergences give
The dual characterization of variation implies |\nu|\le2\,dt\,dw. The Radon–Nikodym theorem therefore gives a measurable function
such that
for every compactly supported continuous \Phi on the product. Here and henceforth limits in x may use the fixed subsequence.
Boundedness also permits replacing the compactly supported continuous tests in (2.22) by the indicator of 0<t<1: truncate near 0, approximate the remaining interval at its endpoints, and use the uniform bound on both weighted counting measures and W. Equation (2.20) therefore implies
Approximating this interval indicator by nonnegative smooth functions supported in (0,1), we can fix a real nonnegative \phi\in C_c^\infty((0,\infty)) with
The rest of the proof derives a contradiction from this fixed profile and bump. Every auxiliary choice will be made after J,f_x,g_x,F_x,W,\phi and the subsequence have been fixed.
3 Arithmetic preliminaries at an auxiliary log scale
This section supplies local asymptotic formulae and upper bounds for the coefficient and residue weights used in the amplification. All limits in this section are as B\to\infty. Constants may depend on explicitly fixed compact scale ranges, on the finitely many smooth norms indicated below, and later on the fixed regularity grid and its tolerance. They are uniform in the integer variables and moduli in the stated ranges. The parameter B will always be held fixed when an inner limit in x is taken elsewhere in the proof. We use the notation e(t)=\exp(2\pi i t).
Take B through sufficiently large positive integers and put
In particular R\to\infty, \ell/\log B\to1, and T<P_0. An integer is rough if it has no prime divisor at most P_0. Write \mu_{\rm Mob} for the Möbius function, \omega for the number of distinct prime divisors, and \omega_E for this count restricted to a set of primes E.
The factors 2^{-\omega} turn divisor sums into averages over fair splits of prime sets. Set
The second definition also applies to v\in\whZ, and to a subset S\subset\mathcal P, by taking \omega_{\mathcal P}(S)=|S|. For U\subset S\subset\mathcal P, let a_U=\prod_{p\in U}p, with a_\varnothing=1. The definitions give
A fair split selects each prime of S independently with probability 1/2. Thus summing the left side against a function of U gives B times its fair-split expectation.
The coefficient supports used below are contained in [1,\exp(bB)] for some fixed b<4 once B is large. Thus every prime divisor of a rough coefficient on these supports belongs to \mathcal P.
3.1 Uniform local asymptotics
Our local estimates have two outputs. For A_0, they give a smooth mean on multiplicative windows at log scale B, including additive phases with moduli and real frequencies bounded by fixed powers of B. For a product a formed by selecting each p\in\mathcal P independently with probability z/p, where z\in\{1/4,1/2\}, they give a smooth density for \log a/B after restriction to a unit residue class, with an absolute error useful even on intervals of width O(1/B) in that coordinate. Both outputs follow by partial summation from cumulative estimates with a saving of any prescribed power of B. We first recall the unrestricted Selberg–Delange estimates, then exclude the primes at most P_0 uniformly as that cutoff moves. For these two values of z, define
Lemma 3.1 (Classical estimates used in roughness removal). For each fixed nonnegative integer H and either of the above values of z, there are real constants c_j(z) such that, for Y\ge3,
where
For each fixed C,D>0, uniformly over nonprincipal Dirichlet characters \chi of modulus d\le(\log Y)^C, one has
The constants in the second estimate, and the threshold after which it holds, need not be effective.
Proof. The first statement is the classical fixed-order Selberg–Delange expansion; see [11, Theorem 1] and [14, Theorem 13.2]. The normalization and the moving roughness cutoff required here are recorded explicitly below. In \Re s>1,
Define the local powers by their power-series logarithms. The logarithm of each local factor of G_z is O(p^{-2\Re s}). Consequently G_z is analytic, nonzero, and bounded on \Re s\ge0.9, with all derivatives bounded on fixed smaller compact sets. Near s=1, put u=s-1. The analytic factor
has a convergent Taylor series and has value G_z(1) at u=0. Truncated Perron inversion, followed by a contour around the cut to the left of 1, integrates its jth Taylor term against Y e^{u\log Y}u^{j-z}. Hankel’s reciprocal-gamma formula gives the factor (\log Y)^{z-j-1}/\Gamma(z-j). Taylor’s remainder, integrated on that contour, is O_H(Y(\log Y)^{z-H-2}). For completeness, the contour may have right edge 1+1/\log Y, height \exp(c\sqrt{\log Y}), left edge 1-c'/\sqrt{\log Y}, and small circular part of radius 1/\log Y. The classical zero-free region for \zeta permits fixed sufficiently small c,c'>0; the other contour pieces and the Perron truncation error are O_H(Y\exp(-c''\sqrt{\log Y})(\log Y)^{O_H(1)}) and are absorbed in the displayed remainder. The local expansion just described also identifies c_0(z)=G_z(1)/\Gamma(z).
We spell out the character uniformity. The twisted series is
The same cancellation of the linear local term bounds G_{z,\chi} uniformly in \chi on \Re s\ge0.9. Write L_Y=\log Y and \Theta=\exp(c\sqrt{L_Y}), and use the rectangle
The classical Dirichlet zero-free region excludes zeros in this rectangle except possibly a real zero of a real primitive character inducing \chi. Siegel’s bound states that for every fixed \varepsilon>0 such a zero obeys 1-\beta\gg_\varepsilon d^{-\varepsilon}; see [14, Theorems 12.3 and 12.10] for the zero-free region and exceptional-zero bound. Choose \varepsilon<1/(2C). Since d\le L_Y^C, this distance is eventually larger than c'/\sqrt{L_Y}, uniformly in the allowed moduli. The Euler factors removed for imprimitive characters have no zeros in \Re s>0. Thus an analytic logarithm of L(s,\chi) exists throughout the rectangle, agreeing with its Euler-product logarithm on its intersection with \Re s>1.
There is also a uniform polynomial bound in L_Y on this rectangle. For s=\sigma+it truncate the Dirichlet series at V=\lceil d(2+|t|)\rceil. The periodic character sums have modulus at most d, so partial summation bounds the tail by O(d(1+|s|)V^{-\sigma}). The initial segment is at most O((1+\log V)V^{\max(1-\sigma,0)}). Since \log V\ll_C\sqrt{L_Y} and (1-\sigma)\log V=O_C(1) in the rectangle, these estimates bound L(s,\chi) by a fixed power of L_Y. Because z is real, the modulus of the chosen analytic power is |L(s,\chi)^z|=|L(s,\chi)|^z.
The coefficients have modulus at most one. At an endpoint Y\in\mathbb Z+\tfrac12, truncated Perron therefore has error O(Y(1+\log Y)^2\exp(-c\sqrt{L_Y})); this follows also by summing its usual \min(1,(\Theta|\log(Y/n)|)^{-1}) error. Shift the Perron contour to the left edge. There is no pole or branch cut in the twisted case. The new vertical integral is bounded by Y\exp(-c'\sqrt{L_Y}) times a fixed power of L_Y, and the horizontal integrals have the additional factor \Theta^{-1}. This proves an exponential square-root-log saving and hence the claimed saving of any fixed logarithmic power. For arbitrary Y\ge3, let Y' be the least element of \mathbb Z+\tfrac12 with Y'\ge Y. Then 0\le Y'-Y<1 and d\le(\log Y)^C\le(\log Y')^C. Replacing Y by Y' changes the sum by at most one term and any smooth main term by an amount absorbed in the stated errors. This gives both estimates for arbitrary real Y.
Lemma 3.2 (The moving roughness cutoff). Fix D>0. There is a fixed integer H=H(D) and real coefficients C_{j,z}(P_0), 0\le j\le H, such that uniformly for B^{0.89}\le\log Y\le4B,
There is an absolute constant C_0 such that for every fixed j,
where \gamma_{\rm E} is Euler’s constant. Uniformly for nonprincipal \chi of modulus d\le B^{15} in the same size range,
Proof. Define the multiplicative function h_z by h_z(p^e)=(-z)^e for p\le P_0 and e\ge1, and by h_z(p^e)=0 for p>P_0 and e\ge1. Its Euler factors give the exact identity g_{z,P_0}=g_z*h_z. If \epsilon_0=1/\log P_0, then
Indeed p^{\epsilon_0}\le e in the product, its logarithm is bounded by a constant times \sum_{p\le P_0}p^{-1+\epsilon_0} plus a bounded sum of square terms, and Mertens’ estimate bounds that first sum by O(\log\log P_0). Increasing the absolute constant C_0 if necessary gives the displayed assertion for both values of z. Since (\log v)^k\le k!\epsilon_0^{-k}v^{\epsilon_0}, it also gives
Put L_Y=\log Y. In the convolution sum the terms v>\sqrt Y contribute, after division by Y, at most
because the inner untwisted or twisted sum is at most Y/v in absolute value. For v\le\sqrt Y, apply Lemma 3.1 at Y/v. For the untwisted sum expand each factor by Taylor’s formula:
This remainder is uniform for 0\le\log v\le L_Y/2. After summing with h_z(v)/v, the total Taylor and Selberg–Delange remainders are at most
The moment sums in the polynomial coefficients may be extended to all v. To see that the resulting error is negligible, combine (\log v)^k\ll_k\epsilon_0^{-k}v^{\epsilon_0/2} with the preceding Rankin bound: the tail of each such moment is O_k((\log P_0)^{C_0+k}\exp(-L_Y/(4\log P_0))). Thus explicitly
The moment bounds prove the claimed coefficient bounds. Since \log P_0=1000\log B and L_Y\ge B^{0.89}, choosing the fixed integer H sufficiently large makes all these errors O_D(YB^{-D}). The zeroth moment is \prod_{p\le P_0}(1+z/p)^{-1}. Combining it with the Euler product for c_0(z) gives
The second product tends to one, and Mertens’ product formula proves its stated asymptotic and positivity.
For a nonprincipal character, use the same convolution with h_z(v)\chi(v) and the second estimate of Lemma 3.1. On v\le\sqrt Y we have \log(Y/v)\ge L_Y/2 and, for all large B, d\le B^{15}\le(\log(Y/v))^{18}. Take an arbitrarily large fixed saving exponent in that lemma. The factor \sum_v|h_z(v)|/v\ll(\log P_0)^{C_0} is absorbed by increasing that exponent. The terms v>\sqrt Y have already been bounded independently of \chi. This proves the required uniform character estimate.
We now turn these counting estimates into local densities for the coefficient weights and probability laws for randomly selected prime products. Choose the expansion order once, sufficiently large to use Lemma 3.2 with D=200 for both values of z. For L>0 write
Thus D_{z,B}(\log Y) is exactly the derivative with respect to Y of YP_{z,B}(\log Y). Define
These are finite combinations of smooth powers on s>0. The coefficient bounds and \log P_0=B^{o(1)} imply, for every fixed nonnegative derivative order, convergence of these functions and their derivatives uniformly on compact subintervals of the indicated domains:
where
Here Q_{z,B}\sim(4R)^{-z} by Mertens’ estimate. To check the derivative assertion directly, the j=0 term has the stated limit after normalization. Every term with j\ge1, as well as the P'_{z,B} part, gains at least one power of B^{-1} relative to that term on a fixed compact interval, with only a fixed power of \log P_0 lost. The same reasoning applies after any fixed number of s-derivatives. Moreover the leading term dominates uniformly for Bs\ge B^{0.89}: each ratio of a lower-order term to it is bounded by a fixed power of \log P_0 divided by a positive power of Bs. Consequently f_{z,B}(s)\ll s^{z-1} for B^{-1/10}\le s\le3.2, and all these densities are positive on that range for sufficiently large B.
Proposition 3.3 (Local coefficient and product laws). Let w_3 be smooth and supported in a fixed compact subinterval of (0,\infty). Uniformly for 0.9B\le\log X\le2.2B, q\le B^{15}, (u,q)=1, and real \xi with |\xi|\le B^{14},
The convention q=1 is included. The constant in the error is controlled by a fixed constant times finitely many low-order smooth norms of w_3; the expansion order defining m_B is independent of w_3.
Let \nu_z be the law of the product of primes of \mathcal P selected independently with probabilities z/p, and write s=\log a/B for its log coordinate. For d\le B^{15}, every such product is a unit modulo d. Uniformly for all intervals I'\subset[B^{-1/10},3.2] and unit residues r\pmod d,
Uniformly for 0\le\delta\le1,
For each positive integer n\le\exp(3.2B),
where both sides are zero unless n is a squarefree rough product, apart from the allowed empty product n=1.
Proof. Since P_0>B^{15}, all rough integers are units for every modulus in the statement. Character orthogonality and Lemma 3.2 give, for each unit class,
There is no loss of a factor \varphi(d) here: it is cancelled by the normalization in character orthogonality. Partial summation, multiplication by (\log P_0)R^{1/2} when z=1/2, and summation over the unit residues against e(ur/q) now prove (3.2). The sum of the latter phases is the Ramanujan sum \mu_{\rm Mob}(q) because (u,q)=1. For explicit error accounting, summation over residues costs at most q, the normalizing factor is at most B eventually, and differentiating w_3(t)e(\xi t) costs at most a constant times (1+|\xi|)(\|w_3\|_\infty+\|w'_3\|_1+\|w_3\|_1) on the fixed support. Thus the initial B^{-200} saving exceeds all these losses by much more than the claimed B^{-50}. On that support \log(Xt) is in the range of the preceding lemma once B is sufficiently large.
For a squarefree product n of the allowed primes, independence gives the exact mass
On n\le\exp(3.3B) the last product is 1+O(B/P_0), uniformly: its logarithm is O(\omega(n)/P_0)=O(B/P_0). In this range every rough prime factor is below the upper cutoff \exp(4B). Hence the mass without that last product is exactly Q_{z,B}g_{z,P_0}(n)/n. Partial summation of the unit-class formula between any two endpoints e^{Ba},e^{Bb}, with B^{-1/10}\le a\le b\le3.2, gives
Indeed each endpoint error is O(B^{-200}), and integrating the error O(tB^{-200}) against dt/t^2 over a log interval of length O(B) costs O(B^{-199}); also Q_{z,B}\le1. The O(B/P_0) relative mass correction contributes at most O(B/P_0) in total, since the uncorrected masses are bounded above by the true probabilities. Endpoint atoms have exponentially small mass because n\ge\exp(B^{0.9}). This proves (3.3) for arbitrary endpoint conventions and arbitrarily short or partial intervals. No relative error for a short interval is asserted or needed.
If \delta<1/R, the event s\le\delta forces the product to be empty, so its probability is Q_{z,B}\ll R^{-z}. If 1/R\le\delta\le1, the event forces all primes with \log p>\delta B to be absent. Mertens’ product estimate therefore bounds its probability by
These estimates prove (3.4), including \delta=0. Finally, on a squarefree rough n in the range of (3.5),
uniformly, and also for n=1. This proves (3.5); outside the squarefree rough support both masses vanish.
3.2 Upper sieve bounds with reducing local weights
We state precisely the classical upper-sieve input, in its event-space form. For a fixed positive integer k, choose once a bound P_k>2k depending only on k. For a sieve bound Z\ge2, let \mathcal R_Z\subset\{p:P_k<p\le Z\} be the set of retained primes. Suppose their forbidden local densities obey 0\le\theta_p\le k/p. Mertens’ theorem then gives the upper dimension condition
Let \mathcal V be the ambient mass. For each squarefree d whose prime factors all lie in \mathcal R_Z, let \mathcal V_d be the mass satisfying the forbidden condition at every prime dividing d, and put
Extend r_d by zero to all other positive integers. The classical fundamental lemma of the upper sieve supplies s_k>0, depending only on k, and upper weights of absolute value at most one, supported on squarefree d\le D with prime factors in \mathcal R_Z, such that, when Z\le D^{1/s_k}, the mass avoiding the retained forbidden conditions is at most
The constants are uniform over the forbidden sets satisfying the displayed dimension condition. This is the bounded-dimension upper-sieve statement of [9, Theorems 2.4 and 3.6].
Lemma 3.4 (Interval, rectangle, and random-root sieves). There is a sufficiently small c_k>0, depending only on fixed k, with the following properties for Z\ge2.
In an interval of length N\ge1, at most k forbidden residues at each prime p\le Z give an upper bound
In a rectangle of side lengths N_1,N_2\ge1, suppose that at each prime the forbidden set is a union of at most k proper affine lines. With N_* =\min(N_1,N_2), there is the corresponding bound
An application may omit specified primes from the restrictions, provided it also omits their factors from the products.
Both assertions also apply to reducing local weights. At each prime, attach a factor in [0,1] to each of at most k specified residue classes modulo p in the interval case, or at most k proper affine lines in the rectangle case. The factor is applied on its class or line and equals one off it. Replace 1-\theta_p by the residue average of the product of these factors.
Proof. At a squarefree modulus d, the one-dimensional forbidden intersection has at most k^{\omega(d)} residue classes, each counted with error O(1). Its remainder is therefore O(k^{\omega(d)}). In the rectangle there are at most k^{\omega(d)}d residue pairs: at each prime there are at most kp pairs, and the Chinese remainder theorem multiplies these bounds. Each residue pair has count
Thus its remainder is O(k^{\omega(d)}(N_1+N_2+d)). For fixed k, \sum_{d\le D}k^{\omega(d)}\ll_k D(1+\log D)^{O_k(1)}; one may obtain this by bounding k^{\omega(d)} by a fixed divisor function and applying the elementary hyperbola bound to its sum. Use the preceding upper sieve with D=N^{1/2} in an interval, or D=N_*^{1/2} in a rectangle, and choose c_k<1/(2s_k). The interval remainder is N^{1/2+o(1)}. The rectangle remainder is at most
for sufficiently large N_*. Enlarge the constants to cover smaller lengths.
The preceding sieve application temporarily omitted the primes p\le P_k. For each unweighted choice of forbidden conditions, restore the factors of those primes whose restrictions the application retains. If one such prime forbids the whole residue space, the fully sifted count is zero. Otherwise its surviving fraction 1-\theta_p is at least 1/p in an interval and at least 1/p^2 in a rectangle. The product of the reciprocals of these fractions over the bounded initial set is therefore bounded in terms of k. Enlarging C_k restores all their factors in the displayed main term, without changing the remainder. This argument is uniform when conditions coincide and when Z includes only part of the initial set. Primes that an application chooses to omit remain absent from both its restrictions and its product.
For the weighted assertion, at every prime independently choose whether to forbid each specified condition, using probability one minus its local weight. Make these choices independently between conditions too, even if some coincide. For a fixed integer point, its probability of avoiding all the randomly chosen conditions is exactly the product of its local weights. Apply the unweighted bound for each choice and take expectations. The constants and remainders are uniform because every choice has at most k residue conditions or proper lines. Independence between primes makes the expectation of the local-density product the product of the expected local densities. The latter is precisely the residue average stated in the lemma. The initial-prime factors were restored before this averaging, so no lower bound for an averaged local factor is needed. This proves the weighted version, including coincident conditions. Squarefreeness conditions and all factors in [0,1] above Z may be dropped when applying an upper bound.
In the remaining estimates, n\asymp X and analogous notation mean membership in an interval between fixed positive constant multiples of the indicated scale. Restricting to additional size or positivity conditions only decreases the upper bounds. They are uniform when (\log X)/B lies in any fixed compact subinterval of (0,4), with constants allowed to depend on that subinterval. In particular, they apply throughout 0.9B\le\log X\le2.2B, the range used later. In applications involving TX, this convention still leaves all coefficient logarithms below 4B.
Lemma 3.5 (First and second coefficient moments). On these intervals,
Proof. Choose a sufficiently small fixed c>0 and sieve up to Z=\exp(cB), as permitted by Lemma 3.4 throughout the fixed log-size range. For a single form, local weight zero at p\le P_0 and local weight t\in\{1/2,1/4\} above P_0 give residue averages 1-1/p and 1-(1-t)/p, respectively. Their product is
Dropping squarefreeness only increases the sum. Put H_B=(\log P_0)R^{1/2}. Multiplication by H_B for the first moment gives one. Multiplication by H_B^2 for the second moment gives
The sieve remainders remain negligible after these polynomial factors. The omitted primes above Z up to any of the fixed log-size endpoints have bounded reciprocal sum; in particular using this fixed small c does not alter any power of R in the bound.
Fix a sufficiently large absolute constant C_2 and define, for nonzero integers j,
For every fixed r>0 this function satisfies \sum_{1\le j\le U}\Sigma(j)^r\ll_r U for U\ge1. Indeed expand \Sigma(j)^r=\sum_{d\mid j}b_r(d), with b_r nonnegative, supported on squarefree integers, and b_r(p)=(1+C_2/p)^r-1=O_r(1/p). Then \sum_d b_r(d)/d=\prod_p(1+b_r(p)/p)<\infty, proving the assertion by summing the divisor expansion.
Lemma 3.6 (Two- and three-form coefficient bounds). Uniformly for 0<|j|\le T and squarefree rough b\asymp TX,
On the same fixed log-size ranges,
The implied constants do not depend on b,j,X, or B.
Proof. Use the same sieve limit Z=\exp(cB) with c sufficiently small. For (3.7), at p\nmid jb the roots of c and b+jc are distinct. At a prime at most P_0 the local density of avoiding them is 1-2/p; at a larger prime the residue average of the two weights 1/2 is 1-1/p. Apart from a factor 1+O(p^{-2}), these are the squares of the single-form factors in the preceding proof. Bounded small primes may be omitted. If p\mid j, then p<P_0 and b is a unit at p. Only the root of c is forbidden. Its loss compared with two ordinary roots is at most 1+O(1/p) outside the omitted bounded set. The product of these losses is covered by \Sigma(j) after fixing C_2 sufficiently large. If p\mid b, then p>P_0 and we may drop both local conditions; their reciprocal sum is
Thus these exceptional primes have bounded total cost. Lemma 3.4 now gives density at most C\Sigma(j)(\log P_0)^{-2}R^{-1} in an interval of length comparable to X. Its normalization H_B^2 proves (3.7).
For (3.8), use the rectangle in (b,c) of area comparable to TX^2. At p\nmid j, the equations b=0, c=0, and b+jc=0 are three distinct lines. Their pairwise and triple intersections have density p^{-2}. Inclusion–exclusion, also with the local reducing weights, therefore gives the product of the three single-form averages up to 1+O(p^{-2}). At p\mid j the lines for a and b coincide; since p<P_0, the loss from three ordinary rough exclusions to two is at most 1+O(1/p). Again their product is covered by \Sigma(j). The rectangular sieve gives density at most C\Sigma(j)(\log P_0)^{-3}R^{-3/2}, which is cancelled by H_B^3. All sieve remainders are negligible because X is exponential in B, whereas T, the normalizations, and the possible singular losses are polynomial in B. Extending a support to a rectangle or interval for the sieve is harmless: the local congruence restrictions continue to hold on the original positive support, and the extension is used only for an upper bound.
3.3 Regularity cutoffs and their loss
Fix an integer L\ge1 and let \Delta=1/L. The grid consists of g=i/L, 1\le i\le L. Fix a small \tau>0 and, later, a sufficiently large C_*>0. The choices of L and \tau remain available for the additional fixed requirements in Section 6: first take L sufficiently large, then take \tau sufficiently small. None of the estimates of the present section requires an upper bound for L or a positive lower bound for \tau.
The prefix bounds will control competing divisor representations in Section 6; the tail lower bounds will make the two-split second moment in Section 4 summable.
Definition 3.7 (Regular prime sets). For S\subset\mathcal P put
Let Y_i=2^i\log P_0, 0\le i\le i_{\max}, where i_{\max} is the first index with Y_i\ge4B. The set S is regular if both of the following conditions hold:
and
An integer or profinite integer is regular when its set of dividing primes from \mathcal P is regular. Multiplicities are not counted in these cutoffs.
Put A=A_0\ind_{\rm reg} and K=K_0\ind_{\rm reg}, with the analogous definition for K(S). The lower total-count bound in the definition gives
For A, any prime factors outside \mathcal P only decrease the weight; the additional factor \log P_0 is B^{o(1)}. Choose \tau sufficiently small that
These are compatible strict conditions, since
Any further decrease of \tau preserves them.
Lemma 3.8 (Loss from imposing regularity). There is an absolute c_3>0 such that, for each fixed choice of the grid, tolerance, and compact log-size ranges above, there are C>0 and a function \epsilon_B\to0 such that the part of the untruncated sum in (3.8) where at least one coefficient is not regular is at most
The constant C may depend on the fixed grid, tolerance, and scale ranges, but not on C_*,j,X,B. The function \epsilon_B may depend on the same fixed data but is independent of C_*. The analogous bound with scale X applies to the first-moment sum of A_0 in (3.6). For the product of two independent coefficient weights in a box, it applies with the corresponding area in place of TX^2\Sigma(j).
The same upper probability O(\epsilon_B+e^{-c_3C_*}) holds for failure of regularity in a set of independent prime indicators on \mathcal P with parameters 1/(2p)+O(p^{-2}), uniformly when the constant in the O term is fixed. It also holds after omitting a deterministic subset E_B\subset\mathcal P satisfying
for a fixed C_E>0. The subset may depend on B, and the bound is uniform over all such subsets for each fixed C_E.
Proof. We give direct upper bounds relative to the scales in the statement; no division by the actual mass of a weighted sum is used. Sieve with the fixed Z=\exp(cB) used in Lemmas 3.5 and 3.6. For a coefficient whose count is being tested, replace its local weight 1/2 on a subset \mathcal Q\subset\mathcal P by (1/2)e^s or (1/2)e^{-s}, where s>0 is fixed and small enough that (1/2)e^s<1. The random-root sieve still applies. At ordinary primes the logarithm of its product, relative to the unmodified single-form factor, changes by
The O(1) is uniform for small fixed s. In the three-form rectangle, line intersections alter it by a convergent sum of O(p^{-2}); the factors at primes dividing j are still bounded by \Sigma(j), independently of such s. The one-form case and independent two-variable case have the same conclusion with their respective scale bounds. All modified local weights lie in [0,1], so dropping those above Z preserves the direction of the bound, even for the positive tilt.
For a prefix g<1, take \mathcal Q=\{p\in\mathcal P:\log p\le B^g\}; for g=1 take all of \mathcal P. Mertens’ estimate gives
For example, for g<1 the left side is g\log B-\log\log P_0+O(1) once B is large, and its difference from g\ell is O(\log\log B)=o(\ell). There are only fixed finitely many grid points. The exponential Markov factor for a count exceeding (g/2+\tau)\ell is e^{-s(g/2+\tau)\ell}; the tilted sieve therefore bounds its weighted contribution by the appropriate base scale times
For a count below (g/2-\tau)\ell the corresponding bound is
If the latter threshold is negative the event is empty. Otherwise choose s sufficiently small in terms of the fixed \tau; since both exponential remainders in brackets are O(s^2) and g\le1, both brackets are at most -s\tau/2. Thus every prefix violation saves a fixed positive power of B. A union bound over the grid and the at most three coefficients contributes o(1) times the scale bound.
For a tail endpoint Y=Y_i<B, use the negative tilt on \mathcal Q=\{p\in\mathcal P:\log p>Y\}. Uniformly in these endpoints,
When Y\le cB this is Mertens’ estimate with upper endpoint e^{cB}. When cB<Y<B the sum is zero and \log(B/Y)=O_c(1), which gives the same formula. Exponential Markov at the threshold 0.4\log(B/Y)-C_* gives, relative to the appropriate base scale,
Now choose a small absolute s>0, independently of the grid. The bracket is -0.1s+O(s^2) and is negative. With a_s=\frac12(1-e^{-s})-0.4s>0, the sum of these bounds over the dyadic endpoints Y<B is
For Y\ge B the required lower threshold is nonpositive, so there is no failure. Taking c_3=s proves the asserted tail loss.
The sieve remainders remain negligible in each application: their savings are powers of intervals exponential in B, whereas normalization and Markov factors are only fixed powers of B, and there are O(\log B) tail endpoints. For C_*\ge0, the Markov factors involving C_* are at most their values at zero. Thus the residual function \epsilon_B can be chosen independently of C_*. The prefix factors depend only on the fixed grid and \tau. This proves (3.11) and its one- and two-weight variants.
Finally let X_p be the independent indicators in the probability statement, with parameters \lambda_p=1/(2p)+O(p^{-2}). For either sign and any subset \mathcal Q,
Its logarithm is (e^{\pm s}-1)\sum_{p\in\mathcal Q}\lambda_p+O(\sum_p\lambda_p^2). The latter error is bounded uniformly, while the parameter sums are g\ell/2+o(\ell) for a prefix and \tfrac12\log(B/Y)+O(1) for a tail with Y<B. Omitting E_B changes any parameter sum by at most O_{C_E}(B/P_0)=o(1), uniformly for fixed C_E. Apply exactly the two Markov calculations above, now to this product moment-generating function and with no sieve remainder. This proves all the probability assertions.
4 Amplifying a mixed correlation
Starting from the fixed nonzero correlation profile in Section 2, we construct a nonnegative divisor weight D_B that preserves it. We then expand the weighted correlation so that Cauchy–Schwarz removes g_x and leaves a positive quadratic energy in F_x. The divisor weight depends only on primes tending to infinity with B; its positive mean and bounded second moment are the properties that will preserve the profile.
Retain W, \phi, and
from Section 2, and all parameters and weights from Section 3. In particular, \phi is real and nonnegative. Fix real, nonnegative, nonzero functions \rho_0,\psi\in C_c^\infty((1,2)). The regularity grid and its tolerance \tau are fixed throughout. A constant C_* is also fixed whenever B tends to infinity. Every limit in x below is taken first, along the bad subsequence already selected in Section 2. Constants may depend on these fixed functions, the labels, and the grid and tolerance; dependence on C_* will be indicated when it matters.
4.1 The divisor weight and the correlation it preserves
For an integer n\ge1, consider the two factorizations
We select c with \log c/B in the support of \rho_0 and a with a/(Tc) in the support of \psi. The weights A(a),A(c) apply to the chosen divisors and K(m),K(l) to the two quotients. Define their normalized divisor sum on the profinite integers by
For integer w=n, this is exactly the sum over the two factorizations above. In \whZ, divisibility means membership in the image of multiplication by the divisor. Multiplication by a positive integer is injective on \whZ, so each quotient in the sum is well defined.
For fixed B, the coefficient support is finite: e^B<c<e^{2B} and Tc<a<2Tc. Every coefficient is less than e^{4B} for sufficiently large B, so every prime of a nonzero coefficient weight belongs to \mathcal P. The modulus \prod_{p\in\mathcal P}p^2 suffices to determine D_B: a coefficient is squarefree, and testing whether p divides its quotient requires at most the residue modulo p^2. Thus D_B is a nonnegative function of finitely many high-prime residues.
Define I_{1,x} by the weighted correlation
For each fixed B, the function \phi(t)D_B(w) is a compactly supported continuous profile test. The convergence in (2.22) therefore gives
The factor 1/B in (4.1) is explained by the fair-split identity (3.1). Each finite prime set contributes a factor B when its divisors are summed as a fair split. For two independent products with law \nu_{1/2}, the first-moment calculation below will show that the smooth size-and-ratio expectation is a positive constant divided by B, up to a smaller error. The two factors B and the external division by B then give a bounded positive mean in that model. The next reduction compares this model with the actual divisor weight and bounds the exceptional cases.
4.2 The moment target and the independent split model
Lemma 4.1 (Moments of the divisor weight). There exist C_0>0 and d_0>0 such that, for each fixed C_*\ge C_0 and all sufficiently large B,
The constant d_0 is independent of C_* and B. In addition, \int D_B\ll1 with a constant independent of C_*.
We prove this lemma after reducing the actual divisor weight to an independent model and establishing the concentration estimate needed for its second moment. A single split supplies the positive mean. Two splits of the same prime sets govern the second moment.
Let S_1,S_2 be independent random subsets of \mathcal P, each formed by including every prime p independently with probability 1/p. Conditional on these sets, split each S_\nu by independent fair coins into a coefficient subset \mathcal C_\nu and a remaining subset \mathcal R_\nu. Write
with empty products equal to one, and define
In particular, 0\le\widetilde D_B\ll B pointwise.
Lemma 4.2 (Reduction to independent fair splits). For each fixed C_*\ge0, as B\to\infty,
Proof. For Haar distributed w, let
At each prime these are disjoint hits, each of probability 1/p. Their joint law differs by O(1/p^2) in total variation from two independent Bernoulli(1/p) indicators. Independence across primes therefore couples them to the independent sets S_1,S_2 above, with total failure probability
The probability that any p\in\mathcal P has p^2\mid w or p^2\mid w+1 is also O(1/P_0).
On the complement of these exceptional events, coefficient divisors are subset products of the corresponding site sets, and the prime set of each quotient is exactly the complementary subset. By (3.1), a divisor and its complement then have untruncated weight B2^{-|S_\nu|}. The truncated weight inserts exactly the regularity indicators for those two subsets. Summing the two fair splits shows that the value of (4.1) is precisely (4.5) on this successful coupling.
We can discard the exceptional events in both moments. Any nonzero representation in (4.1) forces each entire site to have at most (1+2\tau)\ell distinct primes, by the total regularity cutoffs for the coefficient and quotient. This remains true in the presence of squares: their two prime sets still cover the site’s distinct primes, although they need not be disjoint. Hence there are at most 2^{2(1+2\tau)\ell} coefficient choices across the two sites. Combining this with (3.9) gives, for example, the uniform bound D_B\ll B^4. Together with \widetilde D_B\ll B, the coupling and site-square errors change its first two moments by at most O(B^8/P_0)=o(1). This proves the comparison.
4.3 The two-split question and an addition-product estimate
The second moment of (4.5) involves two conditionally independent fair splits of the same two site sets. Denote their coefficient products by (a^{(h)},c^{(h)}), h=1,2, and their coefficient and remaining prime sets by \mathcal C_\nu^{(h)},\mathcal R_\nu^{(h)}, \nu=1,2. Choose fixed closed intervals I_{\rho_0}\subset(1,2) and I_\psi\subset(1,2) containing the supports of \rho_0 and \psi, respectively. Let \mathcal H_h be the size-and-ratio event
and let \mathcal E_h be \mathcal H_h together with regularity of its four subsets. Since the smooth weights are bounded and nonnegative,
It therefore suffices to prove the global probability bound \Prob(\mathcal E_1\cap\mathcal E_2)\ll_{C_*}B^{-2}.
To prove this target, we will group the changes between the two splits by their largest logarithmic scale Y. A further unconditional coupling will replace the first coefficient and remaining classes by independent prime processes, with its error paid before conditioning. In that comparison model, the additions from a remaining set at primes with \log p\le Y are independent selections with probabilities 1/(4p), independent also of the data above Y. After fixing the retained coefficient primes and the additions at the other site, the second ratio window confines the logarithm of the recipient’s addition product to an interval of fixed length. A new prime with logarithm above Y/2 also forces that product logarithm above Y/2. The next estimate gives the resulting O(1/Y) probability uniformly in the interval’s location. The second-moment proof will combine it with the retained first-remainder tail restrictions and the high assignment coins. The product itself need not be bounded by the largest allowed prime.
Lemma 4.3 (Addition-product concentration). Fix H>0. Write L=\log P_0. For sufficiently large B, let L\le Y\le8B, put U=\min(Y,4B), and form a random product Q_Y by including each prime P_0<p\le e^U independently with probability 1/(4p). Uniformly over all intervals J\subset\R of length at most H,
The implicit constant is independent of B, Y, and J.
Proof. If the intersection is empty there is nothing to prove. Otherwise enclose it in an interval [v,v+H] with v\ge Y/2, and set X=e^v. The probability of a squarefree product n of the permitted primes is
Set w_Y(n)=0 for other integers. Since Y/2\le U\le Y and U\ge L, Mertens’ estimate gives
Let c_{\mathrm{s}}>0 be an admissible exponent for the one-dimensional upper sieve of Section 3, with a remainder O(N^{.8}) on intervals of length N. Choose a fixed c>0 sufficiently small that c\le1/4 and 2c<c_{\mathrm{s}}, and put Z=e^{cY}. Then Z\le e^U and, since X\ge e^{Y/2}, Z\le X^{c_{\mathrm{s}}}. Dropping squarefreeness, the restriction on prime factors greater than Z, and the reducing weights above Z majorizes w_Y(n) by
Apply the random-weight form of that sieve on an interval containing [X,e^H X] and of length comparable to X, with constants depending only on H. It yields
where
If Z\ge P_0, the relation 1-a_p=3/4+O(1/p) and Mertens’ estimate imply
Consequently q_Y\mathcal D\ll_c1/Y. If Z<P_0, ordinary rough exclusion instead gives \mathcal D\ll1/\log Z=1/(cY), and the same conclusion follows from q_Y\le1. Finally,
Using 1/n\le1/X on the summation interval proves
as required.
4.4 The first and second moments
Proof of Lemma 4.1. By Lemma 4.2, it suffices to prove the asserted mean and second-moment bounds for \widetilde D_B.
The first moment. Without the regularity indicator in (4.5), the products a,c are independent and each has law \nu_{1/2}. Let f_B=f_{1/2,B} and f(s)=c_{1/2}s^{-1/2} on the compact positive log ranges under consideration. For fixed s=\log c/B on the support of \rho_0, (3.3) and partial summation give, uniformly there,
To justify the use of (3.3), the relevant interval in \log a/B has length O(1/B); its absolute distribution-function error is O(B^{-80}), and partial summation against the smooth window, whose total variation is bounded, leaves an error o(1/B) before the displayed multiplication by B. Since \log T/B\to0 and f_B converges uniformly with derivatives on these compact intervals, another application of (3.3) to c shows that the untruncated first moment tends to
The same calculation, or its upper-bound version for fixed intervals containing the supports, shows that the size-and-ratio event \mathcal H_1 has probability O(1/B) under the independent coefficient-product law.
We next control the regularity losses in this normalization. Cover the coefficient support by O(B) dyadic-size boxes c\asymp X, a\asymp TX. All their logarithmic scales lie in a fixed compact subinterval of the ranges for the arithmetic estimates. From (3.5), the joint product probability at (a,c) is bounded by
Within one such box ac\asymp TX^2. The independent-coefficient version of (3.11) bounds the untruncated weighted sum where either coefficient is nonregular by
After the harmonic denominators, summing the O(B) boxes, and multiplying by the B in (4.5), the coefficient-regularity loss is therefore o(1)+O(e^{-c_3C_*}).
Conditional on a selected coefficient subset at a site, the remaining indicators at primes not selected for that coefficient are independent, with probabilities
The selected coefficient primes have reciprocal sum O(B/P_0), uniformly on the coefficient support, because the logarithm of their product is O(B). Thus the independent-indicator regularity estimate of Section 3 applies uniformly after these primes are omitted. The conditional chance of a remaining subset being nonregular is o(1)+O(e^{-c_3C_*}). Multiplying by the bounded smooth weights and the coefficient-event probability O(1/B) shows that the remaining-subset loss in (4.5) is again o(1)+O(e^{-c_3C_*}) after its outside factor B.
It follows that
where the error constant in the exponential term does not depend on C_*. This proves the asserted positive lower bound after choosing C_0 large, for instance with a fixed d_0<d_*/2 and then allowing the negligible coupling error. The upper bound \int D_B\ll1 follows by omitting all regularity indicators in the independent model. Both bounds can use constants independent of C_*. For the lower bound one may also note that increasing C_* only relaxes the tail cutoffs.
The second moment. We use the two-split notation introduced before Lemma 4.3. By (4.6), the required bound is the global probability estimate stated there.
Compare the two assignments of each site prime. If there is a change, its largest logarithm lies in one of the disjoint intervals (Y/2,Y], where
Here 4B\le2^{i_{\max}}\log P_0<8B for large B. Write \mathcal A_Y for the event that this is the largest changed interval. Every change in it is either a move from remaining to coefficient or a move in the reverse direction. The joint law and \mathcal E_1\cap\mathcal E_2 are invariant under exchanging the splits. Hence
where \mathcal U_{Y,\nu} requires at least one prime at site \nu with logarithm in (Y/2,Y] to move from the first remaining set to the second coefficient set. This orientation inequality has been taken in the original symmetric two-split law.
For the upper bound on its right side, couple the four first-split sets \mathcal C_\nu^{(1)},\mathcal R_\nu^{(1)} to four mutually independent prime processes, each with inclusion probabilities 1/(2p). At a prime the two classes at one site were mutually exclusive, so the cost of this coupling is O(1/p^2), and the total cost is O(1/P_0). Assign independent fair second-split coins to each occurrence in these processes. On the successful, collision-free coupling this constructs exactly the original second split. On the exceptional event there may be two occurrences of a prime, for which we still assign independent coins and define coefficient products with multiplicity. This provides a convenient coupled model for upper bounds. Even if the coupling error is counted separately in every one of the O(\log B) intervals, its contribution after multiplication by B^2 is O(B^2\log B/P_0)=o(1). No uniform coupling assertion conditioned on a rare coefficient value is needed.
Work now in that independent model. Its first coefficient products have independent \nu_{1/2} laws, so the first-moment calculation gives \Prob(\mathcal H_1)=O(1/B). Fix first coefficient sets satisfying \mathcal H_1 and the first coefficient regularity conditions. For each term on the oriented right side, we will retain the needed first-remainder restrictions while bounding its second ratio condition. The sum of these conditional bounds over the changed scales, together with the no-change contribution, must be O_{C_*}(1/B) uniformly in the fixed coefficient sets. The orientation factor and coupling error remain outside this conditional calculation.
For a prime set S let N_S(>Y)=\#\{p\in S:\log p>Y\}, and put
The first coefficient tail cutoffs give N_{\mathcal C_\nu^{(1)}}(>Y)\ge q(Y). Expose the first remaining sets above Y, and retain the two necessary tail restrictions N_{\mathcal R_\nu^{(1)}}(>Y)\ge q(Y). Conditional on all these first high-prime sets, the chance that none of their second assignments changes is exactly
On the retained restrictions this is at most
If q(Y)<0 this upper bound exceeds one, which remains a valid bound. Averaging over the first remaining high-prime sets does not increase it.
All first remaining restrictions below Y may now be omitted. For each site, a prime below this threshold is newly added to the second coefficient exactly when it lies in the independent first remaining process and its second coin selects the coefficient. These new-addition indicators are independent and have probabilities 1/(4p). The new additions at the two sites are independent of one another, of the first coefficient sets and their second coins, and of all the exposed variables above Y.
Fix a recipient site \nu. Condition on the retained first-coefficient primes at both sites and on the additions at the other site. The second ratio condition in \mathcal H_2 then restricts the logarithm of the addition product at site \nu to an interval of length at most
For example, for recipient site 1 the second coefficient products have the form a^{(2)}=a_{\mathrm{ret}}b_{\mathrm{new}} and c^{(2)}=c_{\mathrm{ret}}c_{\mathrm{new}}, and solving a^{(2)}/(Tc^{(2)})\in I_\psi gives precisely such an interval for \log b_{\mathrm{new}}. The same calculation with the inequality inverted applies at site 2. On \mathcal U_{Y,\nu} there is a new prime with logarithm greater than Y/2, so this addition product also has logarithm at least Y/2. There are no new additions above Y on \mathcal A_Y.
We can drop the second coefficient size restriction and all second regularity restrictions for this upper bound. Lemma 4.3 then bounds the conditional chance of the remaining addition-product conditions by O(1/Y), uniformly in every value on which we have conditioned. To make the conditioning order explicit, write \mathcal C for the fixed first coefficient sets, G_Y for the retained first remaining tail restrictions, and H_Y for the event of no change above Y. Let \mathcal F include \mathcal C and reveal all second coins of the first coefficient sets, all first remaining data and second coins above Y, and the additions at the other site. The recipient addition product Q_\nu below Y is independent of this information, and the ratio condition specifies an \mathcal F-measurable interval J(\mathcal F). For the oriented event under consideration, the tower property gives
In the last step the high second coins are averaged after the uniform small-ball bound is applied; no conditional bound on \Prob(H_Y\mid\mathcal F) is asserted. Thus, conditional on any good first coefficient sets, the contribution for this orientation at scale Y is at most
The constants here may depend on the fixed C_*, but not on the first coefficient sets, B, or Y.
If there is no change at all, use the tail cutoff at Y=\log P_0. All four first subsets then have at least .4\log R-C_* primes. The same calculation bounds the conditional probability, retaining the first remaining tail restrictions, by
The dyadic scales satisfy
because \alpha_0>1 and the largest Y is less than 8B. Moreover,
Requiring first coefficient regularity only decreases the O(1/B) mass of \mathcal H_1 established above. Combining the preceding bounds, including the orientation factor and the coupling errors, gives
Multiplication by B^2 proves \E\widetilde D_B^2\ll_{C_*}1. Lemma 4.2 transfers these bounds to the Haar divisor weight and completes the proof of (4.4).
4.5 The correlation survives the divisor weights
Lemma 4.4 (Preservation of the profinite profile). For each fixed C_*\ge C_0, put H(t,w)=\phi(t)W(t,w). Then
Proof. The function H is bounded and supported on a fixed compact interval in t, so it is square-integrable. Conditional expectations with respect to t and a finite residue coordinate w\bmod q approximate H in L^2 as these residue coordinates increase. Equivalently, for every \varepsilon>0 there is a function H_q(t,w) depending only on t and w\bmod q such that
This follows, for example, by first approximating in the dense space of finite sums of products of L^2 functions of t and locally constant functions of w, and then taking conditional expectation.
For all sufficiently large B, no prime dividing q belongs to \mathcal P. The finite-residue function D_B is therefore independent of w\bmod q under Haar measure. Consequently
By Cauchy–Schwarz and (4.4), the error on replacing H_q by H is O_{C_*}(\varepsilon), uniformly in large B; the length of the fixed t-support is absorbed in the constant. Since \varepsilon is arbitrary, this proves (4.7).
The factor \int D_B\,dw in (4.7) is real, nonnegative, and at least d_0 eventually. Taking complex absolute values in (4.3) and using (4.7) therefore gives
The possible dependence of the L^2 constant on C_* is harmless: this approximation is performed with C_* fixed, and the positive lower constant in (4.8) is independent of it.
4.6 A positive quadratic energy and its diagonal
The preserved correlation now has an expansion suited to Cauchy–Schwarz. For c\mid am+1, put l_a=(am+1)/c. At fixed B, the coefficient list in (4.1) is finite. Thus g_x(am)=g_x(m) holds simultaneously for every coefficient a on that list once x is sufficiently large, by (2.6). Expanding (4.2), writing n=am, and using this fixed-multiplier invariance gives the exact identity
The values of F_x are unchanged in this reindexing. The expanded form places g_x(m) outside the inner sum, where |g_x(m)|=1 supplies the unit factor in Cauchy–Schwarz.
Proposition 4.5. There is c_5>0, independent of all sufficiently large fixed C_*, for which the nonnegative energy below satisfies the displayed lower bound:
Its diagonal contribution is negligible:
Here I_{2,x}^{\mathrm{diag}} denotes the terms with equal coefficient indices on expanding the square, and l_a=(am+1)/c as in (4.9).
Proof. Choose 0<\alpha_\phi<\beta_\phi<\infty with \operatorname{supp}\phi\subset[\alpha_\phi,\beta_\phi], and write u_- =\inf I_\psi, u_+=\sup I_\psi. If the inner sum in (4.9) is nonzero, then
Let \mathcal I_{c,x} denote this interval. Use the nonnegative weights x^{-1}\rho_0(\log c/B)A(c)K(m) on this interval. Cauchy–Schwarz gives
where |g_x(m)|=1 supplies the unit factor. No multiplicativity of the centered function F_x is needed.
For fixed B, the weight K_0 is periodic and has mean
Progression counting, K\le K_0, and the length of \mathcal I_{c,x} therefore imply
For the last bound, partition the compact log support of \rho_0 into O(B) dyadic-size boxes and apply (3.6) in each box. Thus we may fix C_4>0, independently of C_*, such that
for all sufficiently large B. Combining this with (4.8) proves (4.10), with any fixed
This makes the uniformity of the positive lower constant explicit.
For the diagonal, set
where a ranges over the coefficient support and l over positive integers for which the truncated weights are nonzero. The total-count cutoff and (3.9) give
using the strict inequality 2(h_0+\tau\log2)<.32. Since all smooth weights here are nonnegative,
Bounding one of the two factors A(a)K(l_a) by Q_B and |F_x(am+1)|^2 by 4 yields
where
The same divisor reindexing as before gives
Here no label is present, so finite progression counting directly gives
by the first-moment upper bound in Lemma 4.1. It follows that
which completes the proof.
5 From mixed amplification to an independent-site kernel
The mixed amplification has eliminated the unit-modulus label g_x by Cauchy–Schwarz. Its positive square I_{2,x} contains only the centered label F_x. We first turn its off-diagonal terms into edges between integers at small additive distance. We then separate the residue data at the endpoints from the additional residue data in each representation of an edge. Throughout this section, all parameters other than B and x are fixed; x tends to infinity first. Constants are uniform when the smooth scale variable belongs to the compact range specified below.
5.1 The change of variables
Consider distinct coefficients a,b in the inner square defining I_{2,x}, for fixed m,c, and put l_a=(am+1)/c and l_b=(bm+1)/c. The congruences imply that m is a unit modulo c and that
They also imply (a,c)=(b,c)=1. Since a,b are rough and |j|\le T<P_0, we have (a,j)=(b,j)=1, and hence (a,b)=1. For the ordered term in which the a-factor is conjugated, set
For these fixed coefficients, this is a bijective reindexing by the conditions b\mid n' and a\mid n'+j. Indeed, write n'=bz. The latter congruence, together with b=a-jc, gives j(1-cz)\equiv0\pmod a. Thus
is an integer, and substitution recovers both original congruences and both displayed identities. Positive compact scale supports ensure all arguments are positive for large x.
Figure 1 records the two fixed multiplications that produce the additive shift. Only fixed-multiplier invariance is used; the centered function F_x need not be multiplicative.
Figure 1: The exact reindexing of two divisor representations. The coefficient identity makes the new endpoints differ by j, while fixed-multiplier invariance preserves their centered labels.
For fixed B, the coefficient supports are finite, so (2.6) applies simultaneously to the multipliers c,b,a once x is sufficiently large. Removing c and then inserting b,a gives
Define
If s=n'/(Tx), u_1=a/(Tc) and u_2=b/(Tc), then
The two original \phi-arguments are therefore interchanged, with errors O_B(1/x). Since they occur as a product, their replacement by \Psi_s has vanishing error for fixed B. There is a fixed compact interval \mathcal S\subset(0,\infty) outside which \Psi_s vanishes on the coefficient supports. It depends only on \phi,\psi.
Consequently, the off-diagonal part of I_{2,x}/(BT) is, up to o_x(1),
where, for u\in\whZ,
All coefficient variables are positive integers. Divisibility in \whZ means membership in the image of multiplication by the divisor; that multiplication is injective. The preceding congruence calculation also proves that every quotient in (5.2) is defined on its summation domain. This kernel is nonnegative, depends on finitely many prime-power residues, and satisfies
For this last identity, exchange a,b: the last quotient is unchanged because c(u+j)-a=cu-b.
Lemma 5.1 (Mean edge mass). Uniformly for 0<|j|\le T and s\in\mathcal S,
The implied constant can be independent of the regularity parameter C_*.
Proof. Replace all truncated weights by their untruncated majorants. For fixed pairwise coprime a,b,c, the two endpoint congruences have Haar probability 1/(ab). At a prime p\in\mathcal P not dividing abc, the three residue weights have distinct zero classes 0,-j,b/c for u. Here p>|j|, and b/c\not\equiv-j\pmod p follows from a=b+jc. Their local mean is 1-3/(2p). At primes dividing abc discard the local reducing factors; this changes the Euler-product bound by at most \exp(O(\sum_{p\mid abc}1/p))=O(1), since that sum is O(B/P_0). Independence over primes and Mertens’ formula give
On a dyadic box c\asymp X, the denominator is ab\asymp T^2X^2. The three-form estimate (3.8) bounds its contribution before the factor 1/B by O(\Sigma(j)/T). There are O(B) boxes. This proves the assertion using only untruncated upper bounds.
5.2 Blocks and the norm used for comparison
Fix 0<\eta<1 and C_6>1, and set M=\lceil C_6T\rceil. Removing the lags |j|<\eta T in (5.1) costs O(\eta)+o_x(1) in absolute upper limit, by Lemma 5.1 and the bounded ordinary averages of \Sigma. Average the origins over i=1,\ldots,M, writing n'=n+i. For fixed B, replacing (n+i)/(Tx) by n/(Tx) has vanishing error. At lag j, the fraction of i for which k=i+j\notin[1,M] is at most |j|/M. The total cost of these endpoints is O(T/M)=O(1/C_6). The remaining expression is
Thus (4.10) and the diagonal estimate give a positive lower bound for the iterated lower limit of (5.4), once \eta is small enough and C_6 is large enough. These choices are made after C_* and before letting B grow.
Call a pair (i,k) allowed if 1\le i,k\le M and \eta T\le|k-i|\le T. All matrices below are zero on other pairs. For a real matrix H, define
The same maximum results from allowing real test coordinates in [-1,1]. Splitting real and imaginary parts shows that for complex z_i with |z_i|\le2,
For fixed B, a matrix whose entries are finite-residue functions continuous in s has the same property after taking this finite maximum. Its ordinary scale averages converge to its Haar-product integral. Therefore bounds on the Haar expectation of the norm, uniformly for s\in\mathcal S, control errors in (5.4). This comparison is deterministic in the labels; it requires no independence between the labels and the residue data.
5.3 Endpoint types and candidate representations
The block energy is now expressed in the norm that will control its approximation. We next separate the prime-divisibility data at the endpoints from the additional residue data belonging to each edge representation.
Put S_i(u)=\{p\in\mathcal P:p\mid u+i\}. We compare them with independent sets S_i, each formed by independently including every p\in\mathcal P with probability 1/p. At a fixed p>P_0>M, the actual law has disjoint hits of probability 1/p at each site. Its total variation distance from independent hits is O(M^2/p^2). Consequently the joint site laws can be coupled with failure probability O(M^2/P_0). Also
For an allowed pair i,k=i+j with j>0, a candidate consists of a subset product b of S_i, a subset product a of S_k, and the positive integer c=(a-b)/j. Require pairwise coprimality, rough squarefreeness, all three coefficient regularity conditions, and regularity of the two remaining sets S_i\setminus b and S_k\setminus a. Here S\setminus b means removal of the primes dividing b. It is harmless to use the closed support windows
the smooth factors still impose the original supports. A reversed ordered pair refers to the same candidate.
A contributing endpoint has at most (1+2\tau)\ell primes. There are at most 2^{2(1+2\tau)\ell} subset choices at a pair, so the number of candidates in the entire block is O(B^4). This rough bound also applies to representations that contribute to (5.2) in the presence of site squares: the union of the coefficient and quotient prime sets covers the site’s distinct primes, and their total-count restrictions give the same bound. Together with (3.9), this gives, for example, a deterministic O(B^{10}) bound for all total matrix masses used below. This bound allows small-probability errors to be discarded before sharper mean estimates are available.
Set k_B=\E_S K(S) under the independent 1/p law. The untruncated Euler product gives k_B\ll1. Define the latent kernel
and extend it by symmetry and by zero on nonpairs. For actual endpoint sets without site squares, the terms allowed by the smooth factors have the same coefficient representations in (5.2) and (5.8), and the two endpoint quotient prime sets are the complementary sets displayed in (5.8). The latter kernel keeps these terms and replaces the remaining factor K(m) by its independent mean k_B.
Lemma 5.2 (Uniform conditional means). For every possible endpoint type S_i, not merely almost every typical type, and every allowed lag j=k-i,
In particular, every conditional expected degree is O(1), and \E\sum_{i,k}\mathcal L_{ik}=O(M).
Proof. For an admissible fair split b at the first endpoint, A(b)K(S_i\setminus b)=B2^{-|S_i|}. At the other endpoint, the analogous identity and then averaging over its site set give the split-product law \nu_{1/2}. By (3.5), its mass at a is at most CA_0(a)/(Ba). Dropping all remaining restrictions for an upper bound yields
using (3.7). This is a restricted expectation of mass at most one, with no division by its probability. If the fixed type has no admissible split, its kernel is zero. The same estimate with signed lag reversed handles either endpoint. Summing the bounded averages of \Sigma proves the degree assertions.
5.4 Separating the auxiliary roots
The following comparison justifies this averaging in expected cut norm, uniformly against a proposed endpoint kernel. It is stronger than an estimate against any one predetermined pair of tests.
Proposition 5.3 (Independent-root comparison). Let \mathcal M_{ik}(S_i,S_k;s) be a symmetric real kernel, zero on nonpairs, with total absolute mass O(B^{10}) uniformly in its arguments. Then
The error is uniform for s\in\mathcal S.
Proof. In the absence of site squares, quotient prime sets at the endpoints equal the complementary sets used in (5.8). For a candidate at i,k=i+j, the remaining argument in (5.2) is
We show that, at a negligible total error, the set of primes dividing this argument can be replaced for each unordered candidate by an independent 1/p set, independent of the site sets and of the other candidates’ extra sets. The following argument first bounds two obstructions determined by the endpoint sets: coincident rational roots and a root forced to hit a third occupied site. It then fixes a surviving actual site configuration and couples the remaining prime tests, without conditioning on absence of site squares. The site-square event is paid for in the matrix weights, and the final step controls the independent extra-weight fluctuations in cut norm.
Coincident rational roots. Since b/c is reduced, equal r for two candidates forces the same denominator c. Given r,c, the coefficient at any position s' is fixed, namely b+(s'-i)c. On the same pair this determines the candidate uniquely. Any other unordered pair with this root uses at least a third position with a prescribed positive coefficient at least Tc. Conditional on the first two independent site sets, that coefficient is available at the third site with probability at most 1/(Tc): it has probability zero unless it is a squarefree product of \mathcal P primes, and otherwise the probability is its reciprocal. The polynomial candidate and position bounds, and c\ge e^B, make the union of these events negligible. The site coupling transfers the conclusion to the actual model.
Forced hits at a third endpoint. Also discard the event that, for some candidate and s'\ne i,k, an occupied prime p at site s' satisfies p\nmid abc and r\equiv-s'\pmod p. In the independent-site model, condition on the candidate’s two endpoint sets. Such a prime divides b+(s'-i)c, a nonzero integer of logarithmic size O(B). It is nonzero because c>1 and (b,c)=1. For any nonzero integer of logarithmic size O(B), the sum of reciprocals of its prime divisors above P_0 is O(B/P_0). Thus the conditional union probability is O(B/P_0) per candidate and third position. A polynomial union bound and the site coupling again suffice.
Coefficient primes and occupied primes. The two structural exclusions above depend only on the endpoint sets, and their actual-law probabilities have been bounded through the site coupling. Fix an actual site configuration avoiding them; its hits at each prime are disjoint. We still do not condition on absence of site squares. At an unoccupied prime, u\bmod p is uniform outside the M forbidden classes -1,\ldots,-M. At an occupied prime, its residue is fixed and the higher p-adic digits remain uniform. These conditional laws are independent over primes.
If p\mid ab, then the coefficients are squarefree and pairwise coprime, and the test p\mid m in (5.11) has conditional probability 1/p, determined by the next digit. If p\mid c, it is impossible. Set these exceptional tests to zero temporarily, in both the actual model and the independent comparison model. The total error per candidate is O(B/P_0). This use of uniform higher digits is made before removing site-square events from the weights; we do not condition those digits on absence of squares.
At p\nmid abc, the root test is u\equiv r\pmod p. If the prime is occupied at an endpoint, such coincidence would force p\mid b or p\mid a. At any other occupied site it is excluded by the preceding discarded event. The actual root test is therefore zero at the remaining occupied primes. The cost of setting the independent test to zero there is bounded in expectation by the deterministic candidate bound times
This domination does not require candidates to be independent of occupied primes.
Unoccupied primes. The roots are now distinct rational numbers. A collision between two of their residues modulo p, after excluding coefficient primes, requires p to divide their nonzero cross-multiplied difference. That integer has logarithmic size O(B). A collision with a forbidden site class has the same bound, or concerns a coefficient prime already handled. For each candidate pair or candidate–site pair, these defective primes have reciprocal sum O(B/P_0). At all such primes, discard all involved tests. Conditional on the sites, each defined test has probability at most 1/(p-M)\le2/p, so another polynomial loss is harmless.
At a remaining unoccupied prime the root classes are distinct and avoid all forbidden classes. Their joint law is a disjoint-choice law with individual hit probabilities 1/(p-M). If there are N_{\rm cand}=O(B^4) tests, its total variation distance from independent Bernoulli(1/p) tests is
For example, compare first to independent tests of probability 1/(p-M), at cost O(N_{\rm cand}^2/p^2) from multiple hits, and then change each probability to 1/p, at cost O(N_{\rm cand}M/p^2). Summing over primes constructs the claimed conditional coupling. The preceding union bounds give total failure probability O(B^{C}/P_0)+O(B^{C}e^{-B}) for a fixed crude exponent C. On these failures, use the deterministic polynomial matrix-mass bounds. After including that loss and enlarging the crude exponent, their contribution to the expected cut norm is at most O(B^{50}/P_0)+O(B^{50}e^{-B})=o(1). Equation (5.7) is handled in the resulting weights, as just explained.
Fluctuations of the extra weights. The preceding coupling has separated the extra roots from the endpoint types. It remains to show that their independent fluctuations are small even after maximizing the testing signs. The comparison model has independent endpoint types and an additional independent set S_{\rm root} for each unordered candidate. In its weight, replace k_B in (5.8) by K(S_{\rm root}). Conditional on the endpoints, the candidate weights are independent, and their means give precisely \mathcal L. By (3.9), each full candidate weight, including its six truncated factors and the factor 1/B, is at most
for large B, with harmless enlargement of constants. For fixed sign vectors in (5.5), an unordered candidate has sign coefficient of absolute value at most two. Positivity bounds the conditional variance sum by a constant times B^{-0.07} times \sum_{i,k}\mathcal L_{ik}.
Bernstein’s inequality, union over at most 2^{2M} sign choices, and integration of the tail show that the conditional expected cut norm of the centered fluctuation is at most
Indeed, before division by M, a threshold
has tail O(e^{-y}) for y\ge0, with C absorbing the sign enumeration. Lemma 5.2 and Jensen’s inequality make the expectation of (5.12) tend to zero. The triangle inequality now proves (5.10); the deterministic polynomial mass bounds control the coupling failures for both kernels. All estimates used only uniform bounds for the smooth factors on \mathcal S.
6 A second moment for the latent rows
The independent-root comparison leaves the latent kernel \mathcal L of (5.8). Its conditional first moments are bounded uniformly over every site type by (5.9). For the sampling argument we also need an integrated second-moment estimate. A small bound on each individual representation does not suffice, because an edge may have several representations. Expanding the square and weighting one representation will identify the measure under which that multiplicity must be controlled.
The grid size L and tolerance \tau will be chosen once below, consistently with Section 3. In every limit B\to\infty in this section, those choices, \eta>0, the block constant C_6, C_*, and the smooth weights are held fixed. All estimates are uniform in the positions and in the smooth parameter s on the fixed compact range used in Section 5. Constants may depend on the fixed parameters but not on the particular first representation.
Proposition 6.1 (Integrated row moments). For a sufficiently fine fixed regularity grid and then a sufficiently small fixed tolerance, the independent-site latent kernel satisfies
Moreover, its normalized total mass has bounded second moment:
For every set I\subseteq\{1,\ldots,M\}, the same estimates hold after replacing \mathcal L_{ik} by \ind_{\{i,k\in I\}}\mathcal L_{ik}; the normalization remains M.
Write h_\tau=h_0+\tau\log2. There are five truncated weights in an individual summand of (5.8). Since k_B\ll1 and the smooth factors are bounded, (3.9) gives the uniform bound
6.1 The measure obtained from a first representation
Fix an allowed pair i,k=i+j. Let \mathcal C_j be the finite set of positive triples (a,b,c) satisfying
whose entries are pairwise coprime, rough, squarefree, and regular. These are precisely the coefficient conditions for a candidate; the two remainder regularity conditions still depend on the site types. We initially take j>0; the negative case follows by exchanging the endpoints. Fix (a,b,c)\in\mathcal C_j. For an integer v whose prime factors belong to \mathcal P, write \mathcal P(v) for its set of prime factors.
In the independent-site model, the event \mathcal P(b)\subset S_i, \mathcal P(a)\subset S_k has probability 1/(ab). Conditional on that event, put
These sets are independent, and at each prime not excluded by the corresponding coefficient the inclusion probability is 1/p. Weighting one such inclusion by its factor 1/2 in K_0 changes this probability to
Thus weighting by K_0(\mathcal T_b)K_0(\mathcal T_a) gives a product probability measure, denoted by \Prob^{\mathrm{tilt}}_{a,b}, under which the two remainder sets are independent and their available prime indicators have probabilities 1/(2p-1).
For a coefficient v the normalizing factor is
The full product with no exclusions is bounded by Mertens’ estimate. Furthermore \log v=O(B) and every prime of v exceeds P_0, so
Removing these factors changes the product by 1+o(1). Consequently \Xi(v)\ll1 uniformly for the coefficients under consideration. For every nonnegative function H of the two remainder sets we therefore have the exact change-of-measure identity
The indicators that the two first remainders are regular will stay inside H. In particular, we never divide by their probability.
Given these remainder sets, reconstruct S_i=\mathcal P(b)\cup\mathcal T_b and S_k=\mathcal P(a)\cup\mathcal T_a, and let N_{a,b,c}(\mathcal T_b,\mathcal T_a) be the number of valid candidates at this pair for the reconstructed types, including the first triple whenever it is valid.
We can now see exactly how this measure enters the square. Expand the square of the sum of nonnegative candidate contributions, designate one candidate as the first representation, and bound every alternative contribution by (6.2). The first contribution retains the two factors K_0(\mathcal T_b)K_0(\mathcal T_a) and their regularity indicators. The change-of-measure identity gives
The implied constant absorbs k_B and the bounded smooth factors. Thus the remaining multiplicity question is the following uniform estimate; the coefficient sum will then be bounded by (3.8).
Lemma 6.2 (Weighted representation multiplicity). The grid and tolerance can be chosen so that, uniformly for (a,b,c)\in\mathcal C_j and \eta T\le |j|\le T,
Proof. Every alternative candidate has a unique decomposition
Here all the products are squarefree, and y is coprime to b while z is coprime to a. The coefficient c' is determined once the four products are chosen. We may discard any of the alternative candidate conditions for upper bounds; however, we retain the coefficient regularity conditions that are used below. Since a',b'\le2T\exp(2B), we have \log y,\log z\le3B for all sufficiently large B.
Set \Delta=1/L, g_0=3\Delta, and U=\max(\log y,\log z). We count the alternatives with U\le B^{g_0} directly from prefix regularity. When U>B^{g_0}, fixing the omissions and the new product at one endpoint places the other new product in one residue class modulo |j|, through e_1z-d_1y=jc'. The resulting progression density is the gain that will pay for the remaining subset choices.
For a grid point g<1, define
and write \omega_g(v)=|\mathcal P(v)\cap\mathcal Q_g|, with the same notation for a prime set. Regularity gives
for each of the first and alternative coefficients, and for each regular first remainder. Mertens’ estimate, on this fixed grid, gives
The o(\ell) is uniform over the finitely many grid points.
Omissions above an addition prefix. Suppose that all primes of z and y lie in \mathcal Q_g. Let D_a=\mathcal P(a)\setminus\mathcal P(e_1) be the primes omitted from a. Regularity of the total counts of a,a' gives
Regularity at g gives the analogous inequality
Subtracting shows that at most 4\tau\ell primes above the prefix can be omitted. The same conclusion holds for the omissions from b. When g=1 there are no primes above the prefix.
Write
with the endpoint values defined by continuity. For completeness, if m\le8\tau\ell, the number of such subsets is at most 2^m\le2^{8\tau\ell}. For 8\tau\ell<m\le(1/2+\tau)\ell, the binomial bound
applies: H is increasing up to 1/2, and mH(k/m) is increasing in m for fixed 0<k<m. Thus the choices at both coefficients together cost B^{\varepsilon_{\mathrm{high}}(\tau)+o(1)}, where \varepsilon_{\mathrm{high}}(\tau)\to0 as \tau\to0. The estimate is uniform also when the relevant set is empty.
Small additions. If
all additions lie in \mathcal Q_{g_0}. On the two first-remainder regularity events, the four relevant prefix sets—the prime sets of a,b and the two first remainders—have at most (2g_0+4\tau)\ell primes altogether. Allowing arbitrary subset choices there, and then the higher omissions just bounded, gives the pointwise estimate
This also bounds its expectation with the first-remainder regularity indicators. By taking L large and then \tau small, its exponent apart from o(1) can be made strictly smaller than .008.
Large-addition classes and combinatorial choices. For U>B^{g_0} use the classes
where g ranges over grid points. All addition primes again belong to \mathcal Q_g. It suffices to treat the portion of a class in which \log z>B^{g-\Delta}. The portion with \log y>B^{g-\Delta} is estimated by the same argument with the endpoints exchanged; the numeric sieve below permits either sign for its second slope. If both inequalities hold, counting the alternative twice only increases the upper bound.
Define the exact normalized counts and their clipped values by
On the first-remainder regularity events, 0\le r_z^*,r_y^*\le1/2+\tau/g. There are O(\ell^2) possible pairs of integer counts. We estimate one such pair at a time.
The number of omitted primes in the a prefix is r_z^*g\ell+O(\tau\ell), among g\ell/2+O(\tau\ell) available primes. Applying \binom mq\le\exp(mH(q/m)), and summing over the O(\ell) permissible values of q, gives, with the higher-omission factor included,
The function \varepsilon_L(\tau) can be chosen to tend to zero for fixed L. To justify this uniformly in the counts, divide m,q by \ell and use uniform continuity of H on [0,1]; the perturbations are O(\tau/g), and g\ge g_0>0 is fixed. The clipping from r_z^* to r_z changes these arguments by the same amount. Also \ell/\log B\to1, and all polynomial factors in \ell contribute B^{o(1)}. We use \varepsilon_L(\tau) below for a possibly enlarged function with this same limiting property.
The choices of d_1 have the corresponding bound with r_y. Conditional on a regular first remainder \mathcal T_b, the number of its subsets y of the prescribed cardinality is at most
This bound is uniform in that remainder set. We may condition on it and sum over these y while the remainder at the other endpoint still has its independent tilted law.
Availability of a fixed numeric addition. The entropy bounds count the possible omitted prime sets. To control large additions, we also need the probability that each numerically specified product is present in the other remainder set. The next bound keeps the first remainder’s regularity requirement in this probability. For a fixed squarefree z in this class, with \mathcal P(z)\subset\mathcal Q_g\setminus\mathcal P(a), its inclusion probability in \mathcal T_a is
The last bound is uniform because \log z\le3B and all its primes exceed P_0. Conditional on those inclusions, the remaining available indicators in \mathcal Q_g are independent with parameter sum
The excluded primes have reciprocal sum O(B/P_0), so this estimate is uniform in the fixed coefficient and numeric addition. First prefix regularity requires the number of these other inclusions to be at most (1/2-r_z^*)g\ell+\tau\ell.
If X is a sum of independent Bernoulli variables with parameter sum \Lambda, then for t\ge0,
For 0\le k\le\Lambda, minimizing gives exponent -\Lambda+k-k\log(k/\Lambda), with its continuous value at k=0. For k\ge\Lambda use the bound 1, and for k<0 the event is empty. Uniform continuity of the resulting rate, including the endpoints, and the fixed-grid relation g\ge g_0 therefore imply
Here u\log u=0 at u=0. Retaining only prefix regularity on the left gives an upper bound for retaining all of first-remainder regularity, which is what the multiplicity expectation requires.
A harmonic sieve for the numeric addition. We now sum the availability bound over numeric additions satisfying the alternative coefficient relation. The factor 1/z in that bound is the reason for the harmonic normalization below. Fix e_1,d_1,y from the preceding choices. The alternative size conditions imply
with absolute comparison constants; we may enlarge the interval to [Z'/2,2Z'].
For these fixed data and the fixed cardinality class, let \mathcal Z consist of the positive integers z with the following properties:
The congruence makes c'(z) an integer. Every valid alternative in this designated class yields an element of \mathcal Z. The inclusion \mathcal P(z)\subset\mathcal T_a remains the event estimated in (6.5); the two alternative remainder regularity conditions are discarded. Equation (6.5) applies to every z\in\mathcal Z, because each is a possible product in the tilted remainder at the a endpoint. If \mathcal Z is empty there is nothing to prove; otherwise its interval and log conditions give Z'\ge\tfrac12\exp(B^{g-\Delta}).
All of e_1,d_1,y are units modulo |j|, since their prime factors exceed P_0>T. Thus the displayed congruence is one unit residue class. We claim
where r_{\min}\in(0,1/2) is any fixed number. The excess exponent 3\Delta+r_{\min}+\tau\log2+o(1) can be made small by the later choices of grid, clamp, and tolerance.
To prove the deterministic estimate, put \lambda=\max(r_{\min},r_z), so r_{\min}\le\lambda\le1/2. On \mathcal Z the fixed cardinality gives
The membership of (e_1z,d_1y,c'(z)) in \mathcal C_j also gives the upper prefix cutoff for c'(z), and hence
The prefix factor is introduced to supply a second reducing root in the sieve below. At the leading g-scale its saving -g/2 combines with the cutoff cost g\log2/2, leaving -gh_0 in the exponent. The calculation below verifies the root conditions and retains the grid and tolerance losses. Insert these two factors before enlarging the summation domain, and keep only the reducing prime factors up to
Deleting the other reducing factors increases each summand. Since z\ge Z'/2 on \mathcal Z, we obtain the deterministic majorant
The finite congruence product is defined for every integer value of c'(z), including zero. The hard prefix cutoff, the fixed-cardinality condition, and all other candidate restrictions have been removed only in this deterministic sum. Equation (6.5) is applied only to z\in\mathcal Z; the displayed enlargement bounds the weighted sum that results.
For explicit congruence accounting put J_1=|j| and \sigma=j/J_1, and choose a unit z_0 modulo J_1 satisfying the progression condition. Write
The parameter t runs through an interval of length N\asymp Z'/J_1. Its logarithm is at least B^{g-\Delta}-O(\log B). Consequently
so the interval upper sieve of Section 3, in fixed dimension two, applies uniformly.
The displayed product already omits every prime at most P_0, including every prime of j. Among the remaining primes also drop those dividing e_1d_1y. Their reciprocal sum is O(B/P_0), uniformly, since \log(e_1d_1y)=O(B). At each retained prime the two slopes are invertible, and the two roots are distinct. Indeed their determinant is
which is nonzero modulo such a prime. The local weights of the roots are \lambda and 1/2, so the average local weight is exactly
This also explains why no coefficient-height factor enters the sieve: only the number and distinctness of residue roots are used. If one keeps primes dividing j instead, the first form is a fixed unit and the second has invertible slope; dropping them avoids any need for a separate local factor.
The random-weight interval sieve bounds the sum of the retained reducing weights by a constant times
The first term is N B^{(g-2\Delta)(\lambda-3/2)+o(1)}, by Mertens’ estimate. Indeed the reciprocal sum in that product is (g-2\Delta)\log B-\log\log P_0+O(1) =(g-2\Delta)\log B+o(\log B), and the sum of the squared reciprocals is negligible. Discarding the small-prime conditions costs at most powers of \log P_0 relative to their possible sieve factors, and those powers are B^{o(1)}; alternatively, the displayed large-prime product already proves the upper bound directly.
Using z\asymp Z' and restoring the threshold factors, the harmonic normalization of the main sieve bound is N/Z'\asymp1/J_1. The remainder contributes at most
which is negligible uniformly in the class, since g\ge4\Delta and \log N\ge B^{g-\Delta}-O(\log B). The total power of B in the main term is
If r_z^*\le1/2, then r_z=r_z^*, and this power equals
We used -3/2+(\log2)/2=-1-h_0. The clamp contribution in parentheses vanishes when r_z\ge r_{\min} and lies between 0 and r_{\min} when 0\le r_z<r_{\min}, including the value r_{\min} at r_z=0. The grid contribution is at most 3\Delta. If r_z^*>1/2, our choice is r_z=\lambda=1/2; the Rankin factor is then exactly 1 and the same upper bound follows directly with the clipped r_z. These observations prove (6.6). If y is the designated large numeric variable, the identical proof uses the slope -d_1 for c' instead, and its determinant has the same nonvanishing property outside the already discarded coefficient primes.
Combining the bounds and choosing parameters. Condition on the first remainder at the b endpoint. If it is not regular its contribution vanishes. If it is regular, enumerate the choices of d_1,y by the two entropy bounds with r_y, and enumerate e_1 by (6.4). For each such choice, sum the availability bound (6.5) using (6.6). Independence of the other first remainder justifies this conditioning, and every bound is uniform in the conditioned regular remainder. Thus we may average it out without any additional factor.
A direct expansion of H gives the exact identity
The three combinatorial factors have entropy exponents gH(2r_z)/2, gH(2r_y)/2, and gH(2r_y)/2. Adding the probability and sieve exponents therefore bounds the contribution of one class, one orientation, and one count pair, with both first-remainder regularity indicators, by
The tolerance error here includes the preceding \tau\log2 and the finitely many entropy and rate perturbations. The last inequality uses H\le\log2 and 0<g\le1. If the bracket in the first exponent is negative, multiplying it by g still gives a nonpositive number; otherwise its maximum is at most 2\log2-1-h_0=\kappa_1.
Here is an explicit consistent order of choices. First choose L large enough that 6\Delta\log2<.004 and 3\Delta<.01. Next choose a fixed r_{\min}<.01. Finally make \tau small enough that the small-addition exponent is strictly below .008, that
and that all the strict weight inequalities in (3.10) hold. These choices are possible because \varepsilon_L(\tau) and \varepsilon_{\mathrm{high}}(\tau) tend to zero for the fixed grid. They impose no condition on C_*, since only the prefix and total regularity conditions were needed for this estimate.
There are finitely many grid classes and orientations and O(\ell^2)=B^{o(1)} count pairs. Since |j|\ge\eta T\asymp_\eta B^{.32} and
the sum of all the large-addition bounds is o(1). The small-addition bound, with a strict exponent below .008, is O(B^{.009}) after the o(1) in its exponent is absorbed. This proves the lemma, including the first candidate itself when valid.
6.2 Squaring the kernel and averaging the rows
The multiplicity estimate has controlled how many alternative representations survive after weighting a first one. Combining it with the small weight of each representation now gives the required integrated row-square bound.
Proof of Proposition 6.1. For an allowed edge i,k=i+j, apply Lemma 6.2 to (6.3) and use the uniform bound on \Xi. This gives
The remaining coefficient sum is bounded using (3.8). Cover the support of c by O(B) dyadic boxes c\asymp X, so a,b\asymp TX in each box. On such a box, dropping coefficient cutoffs for an upper bound gives
Summing the boxes yields O(\Sigma(j)/T). The same proof works for negative j by symmetry. Consequently
The choice in (3.10) gives \kappa_1-5\tau\log2=1-5h_\tau>.229. Thus the exponent on the right is strictly below -.220 before the o(1) term. Finally
so summing over a row proves (6.1), with room to absorb the o(1) in the exponent.
For the last assertion set D_i=\sum_k\mathcal L_{ik}. Given S_i, the summands with different k\ne i are independent, because the other site types are independent and the roots have already been averaged out. Therefore
The conditional mean is bounded for every S_i by (5.9). The variance identity consequently gives
Notice that only an integrated conditional variance bound has been used; a pointwise conditional second-moment estimate is unnecessary. Jensen’s inequality across the rows now gives
For the kernel restricted to I as in the statement, nonnegativity can only reduce the conditional means, row-square sums, and total mass. Keeping the same normalization M therefore gives the stated bounds.
7 Smoothing channels on logarithmic and residue space
The site model admits a useful smoothing operation: choose a fair subset of the primes at one site and record the logarithm and a residue of its product. We prove that this operation suppresses residue dependence in operator norm and that its logarithmic outputs are uniformly approximable on a fixed coarse partition. Operator norm, rather than convergence for each fixed test, is needed because the single-site tests used later may depend on the position and on an externally conditioned sample.
All limits in this section are as B\to\infty. The regularity parameters fixed in Section 3 remain fixed, although no regularity cutoff is imposed in the channels below. We use only the prime-product estimates (3.3)–(3.4) and the independent site law. An occurrence of x inside a channel denotes a logarithmic coordinate, not the original counting scale.
7.1 The channel and its two-split kernel
Let \Omega_B be the finite set of subsets of \mathcal P, with probability measure under which the inclusions p\in S are independent and have probabilities 1/p. Given S, retain each of its primes independently with probability 1/2, and let b be their product. Unconditionally b has law \nu_{1/2}. Write
For a positive integer m_1, partition I into m_1 equal coarse intervals I_l. Choose the number n_B of fine intervals to be
Thus the fine partition refines the coarse partition and \delta_B\asymp B^{-11/10} for every fixed m_1. Use consistent half-open conventions, assigning the final endpoint to the last cell.
For an integer 1\le d\le B, let \mathcal R_d=(\Z/d\Z)^\times with uniform probability measure; for d=1 this is the one-point group. All products in question are units modulo d, since P_0>B for sufficiently large B. Give I\times\mathcal R_d the product measure
For g\in L^2(\Omega_B), define a function constant on each fine logarithmic cell by
The expectation in this definition includes both the site and its fair split. The domain norm of U_d is the site L^2 norm, and its range norm is that of L^2(\lambda_d).
Let P_{\rm av} average the residue coordinate. Then
is independent of d. Let P_{m_1} average on the coarse logarithmic intervals and act identically on the residue coordinate when one is present. Let P_{\rm fine} denote averaging on the fine logarithmic intervals. These averaging operators are orthogonal projections, and P_{\rm fine} commutes with P_{m_1}.
Proposition 7.1 (Uniform channel bounds). For every fixed coarse partition, uniformly for 1\le d\le B,
Moreover, for every \epsilon_1>0, one can choose m_1 such that
All constants are independent of the input g. The sufficiently large threshold for B may depend on the chosen fixed partition.
We first identify the kernel used to prove the proposition. A cell A=J\times\{r\}, with J a fine logarithmic interval, has measure
Set
For a step function F in the range space, the adjoint of the channel is
Consequently U_dU_d^* has the step kernel
This is the density on fine cells of two conditionally independent fair splits of the same site, restricted to I in each logarithmic coordinate. The kernel is nonnegative and symmetric. Its row integral satisfies
By (3.3), the numerator is at most C\delta_B/\varphi(d)+O(B^{-80}). Indeed its logarithmic interval is contained in the fixed compact interval I, where the densities are uniformly bounded. Since \mu_d^{-1}\ll B^{21/10}, the row integrals are bounded uniformly. The column integrals have the same bound. Schur’s inequality gives \|U_dU_d^*\|\ll1, and therefore proves the first assertion of (7.2). This proof already applies to every L^2 input, including signed or complex inputs.
Lemma 7.2 (Independent common and exclusive products). Let b_1,b_2 be two conditionally independent fair splits of the same site. Their joint law can be coupled, with failure probability O(P_0^{-1}), to
where C,E_1,E_2 are independent products with law \nu_{1/4}. Replacing the two-split step kernel by this independent-product step kernel changes its operator norm by O(B^5/P_0), uniformly for d\le B.
Proof. At a fixed prime p, the categories common to both splits, exclusive to the first, and exclusive to the second have probabilities 1/(4p) each, and are mutually exclusive. The joint law of three independent Bernoulli indicators with these marginal probabilities differs from this categorical law in total variation by O(p^{-2}). For example, the probability of two or more independent successes is O(p^{-2}), and each remaining probability differs from its categorical value by O(p^{-2}). Couple these laws independently over the primes. A union bound gives total failure probability
On successful coupling the products agree. Collisions that would put a squared prime in one of the independent products are included in the failure event.
If two joint probability laws differ in total variation by \varepsilon, each cell-pair probability differs by at most a constant times \varepsilon. Their step kernel difference is thus bounded pointwise by O(\varepsilon\mu_d^{-2}). The total measure of the output space is |I|, so Schur’s inequality bounds the operator difference by the same expression times |I|. Now
Taking \varepsilon=O(P_0^{-1}) proves the assertion.
7.2 Removing small exclusive products
The two-split model reduces the channel operator to independent common and exclusive products. An exclusive product near 1 provides too little averaging to erase its residue, so we first bound the operator contribution of those products. Both row and column bounds are needed.
For a product v, write \ell_B(v)=(\log v)/B. Let K_d^{\rm ind} be the independent-product kernel from Lemma 7.2. Its entries are
The following estimate concerns the operator obtained by retaining only the specified event in this probability.
Lemma 7.3 (Two-sided Schur estimate for small exclusives). For 0<\theta\le1/10, the contribution to K_d^{\rm ind} from \ell_B(E_i)\le\theta, for either i=1 or i=2, has operator norm
uniformly for d\le B. The same bound, with a different absolute constant, holds for the union of the two events.
Proof. It suffices to consider i=2. Put
where the last inequality is (3.4). The row integral at A=J\times\{r\} of the restricted kernel is at most
Here E_2 is independent of C,E_1. The marginal law of CE_1 differs from \nu_{1/2} by O(P_0^{-1}) in total variation: the independent common and exclusive indicators can be coupled to their mutually exclusive counterparts prime by prime exactly as in the preceding lemma. Thus (3.3) and \mu_d^{-1}\ll B^{21/10} bound the last display by
For the column integral at A'=J'\times\{r'\}, first omit the condition that CE_1 has logarithm in I. Condition on E_2=e with \ell_B(e)\le\theta. The remaining condition on C is
The shifted interval lies in [2/5,3], has length \delta_B, and the prescribed residue is a unit. Applying (3.3) with z=1/4, uniformly in e, gives conditional probability at most
Integration over the event \ell_B(E_2)\le\theta and division by \mu_d therefore give a column bound C\sigma_\theta+O(B^{-70}). Schur’s inequality proves the claimed operator bound. The i=1 case follows on transposing the kernel. The kernel of the union is nonnegative and is entrywise at most the sum of the two restricted kernels, so the row and column estimates also prove its bound.
The separate column estimate is essential: an estimate for the total probability of a discarded event would not by itself control its operator norm.
7.3 Flattening all nonconstant residue modes
We prove the second assertion of (7.2). Set \theta=B^{-1/10} and retain the part of K_d^{\rm ind} where \ell_B(E_1),\ell_B(E_2)>\theta. For a fixed common product C=c, the probability that one retained exclusive lands in the output cell A=J\times\{r\} is
If the interval is nonempty it is contained in [B^{-1/10},3], since \ell_B(c)\ge0. The interval and its endpoint conventions, including a partial cell at \theta, are within the uniform statement of (3.3). Consequently
The main term depends on J and \ell_B(c), but not on r or on the residue of c. All terms are uniformly bounded: the probability is at most one and its main term differs by O(B^{-80}). Alternatively the bound f_{1/4,B}(t)\ll t^{-3/4} gives the explicit cell bound O(\delta_B B^{3/40}/\varphi(d)).
Conditional on C, the exclusives are independent. Multiplying (7.5) for two output cells and integrating over C, the retained kernel differs from a kernel independent of both residues by at most
pointwise, and hence by O(B^{-70}) in operator norm. A kernel independent of both residues is annihilated by projection onto 1-P_{\rm av} on either side. Lemmas 7.2 and 7.3 therefore yield
because 1/R=(\log P_0)/B=O(\log B/B) and P_0=B^{1000}. Taking the square root of this operator identity gives the stronger bound
In particular (7.2) holds with c_7=1/200. This reasoning did not fix an input function at any stage, so the estimate is uniform on the whole unit ball of L^2(\Omega_B).
7.4 Uniform coarse compactness
Residue dependence is now negligible uniformly in the input function. The remaining task is to approximate the logarithmic output uniformly on a fixed finite partition. This will give a finite family of endpoint features for the graph kernel.
We now prove (7.3). It suffices to use d=1, since u_g=U_1g. Fix 0<\theta<1/20 and choose a smooth function a_\theta:\R\to[0,1] equal to zero on (-\infty,\theta] and to one on [2\theta,\infty). It may be chosen nondecreasing. In the independent-product kernel insert the weight a_\theta(\ell_B(E_1))a_\theta(\ell_B(E_2)). The change is a nonnegative kernel supported where at least one exclusive logarithm is at most 2\theta. Lemma 7.3 bounds its operator norm by
Choose also a smooth upper cutoff equal to one on [0,3] and supported below 16/5. On the positive axis let f_{1/4,B}^{\rm cut} be the product of this upper cutoff, a_\theta, and f_{1/4,B}, extended by zero to the real line. For each fixed \theta, all derivatives of any fixed order of this function are bounded uniformly in B. This follows from the derivative bounds for f_{1/4,B} established before Proposition 3.3; the cutoff keeps the argument away from zero. The upper cutoff changes none of the probabilities relevant to the output interval I.
For completeness, the weighted version of the local law used here follows directly from its interval version. For fixed z=\ell_B(c) and a fine interval J, apply (3.3) to subintervals of (J-z)\cap[\theta,3]. The difference between the exclusive-product measure and the density f_{1/4,B}(t)\,dt has cumulative integral O(B^{-80}) there. Stieltjes integration by parts against a_\theta bounds its weighted integral by O_\theta(B^{-80}): the endpoint values and the total variation of a_\theta are bounded. Thus, uniformly in c,J,
Conditional independence of the two exclusives now identifies the weighted step kernel, up to O_\theta(B^{-70}) in operator norm, with the fine-cell compression of the continuous kernel
Indeed multiplying the two weighted cell formulas makes an O_\theta(B^{-80}) error in each cell-pair probability; division by \delta_B^2 still leaves an operator error smaller than O_\theta(B^{-70}).
The kernel in (7.6) and its first derivatives are bounded uniformly in B, with constants depending on \theta. Differentiation may be taken under the expectation because the cut densities and their derivatives have uniform bounds and the law of C is a probability measure. In particular no limiting law for C, and no derivative bound for that law, is needed. Let \mathcal T_{B,\theta} be the integral operator with this kernel. If a=|I|/m_1 is the coarse mesh, the mean value theorem gives
Here the two superscripts denote averaging the indicated kernel coordinate. Schur’s inequality consequently gives
Write Q=1-P_{m_1}. Fine and coarse averaging commute, and fine averaging is a contraction. Therefore
Combining this with the independent-model comparison and the cutoff estimate proves, for every fixed \theta,m_1,
Given \epsilon_1>0, first choose \theta so that C(2\theta)^{1/4}<\epsilon_1^2/4, and then choose m_1 so that C_\theta/m_1<\epsilon_1^2/4. Taking the upper limit in B and the square root proves (7.3), and completes the proof of Proposition 7.1.
Corollary 7.4 (Coarse site features). For the chosen coarse partition, define
Then 0\le V_l\le |I_l|^{-1}, and for every g\in L^2(\Omega_B) the coarse value of P_{m_1}u_g on I_l is exactly
In particular the bounds (7.2)–(7.3) and this identity hold uniformly when g varies with a position, with B, or with an external parameter.
Proof. Integrating (7.1) with d=1 over I_l sums precisely the fine cells contained in I_l. The result is \E[g(S)\Prob_{\rm split}(x_b\in I_l\mid S)]. Divide by |I_l|. The bounds on V_l follow from its definition; the final uniformity follows because the preceding results are operator bounds rather than fixed-input limits.
8 Integral approximation by endpoint features
We now approximate the latent matrix \mathcal L from (5.8) after integrating over its endpoint types. For an allowed pair k=i+j with j>0, let S_i,S_k be independent site types and let g,h:\Omega_B\to[-1,1] be real measurable functions. The quantity to be approximated is
For a coarse partition supplied by (7.3) at a chosen accuracy \epsilon_1, let V_l be the features from Corollary 7.4. Our target is a finite sum of scalar multiples of
The coefficients may depend on B,j,s,l, but not on the tests. The partition is fixed before B tends to infinity. The comparison will be uniform in the tests, allowing a different function at every position. After summing over allowed pairs and dividing by M, its error will be controlled by the loss e^{-c_3C_*} from removing regularity restrictions, the chosen coarse accuracy \epsilon_1, and a term tending to zero. The final proposition records the constants and their parameter dependence. Section 9 then converts this integrated comparison into control for tests chosen after the whole matrix is sampled.
Throughout this section the regularity grid and its tolerances are fixed, as are C_*, \eta>0, and C_6. The parameter B tends to infinity, T=\lfloor B^{0.32}\rfloor, and \eta T\le j\le T. All estimates involving the smooth parameter s are uniform on the fixed compact interval containing its support. Constants with a subscript \eta may depend on \eta; constants without that subscript in the cutoff-removal estimate below do not. The parameter x from the original counting problem does not occur in this section. The letters x,y below denote log coordinates in I=[1/2,3].
8.1 Removing the regularity restrictions
Let S\in\Omega_B have the independent-site law: each prime in \mathcal P belongs to S independently with probability 1/p. A fair split of S selects each of its primes independently with probability 1/2; write b for the product of the selected primes. The unconditional law of b is \nu_{1/2}. For a real measurable function g on the site space, define the signed mass
In particular, \lvert\gamma_g(n)\rvert\le\nu_{1/2}(n) whenever \lvert g\rvert\le1. All statements below allow g to depend on B.
For a subset product b of S, the untruncated weights satisfy the exact identity
The factor 2^{-|S|} is the conditional probability of each fair split. This identity connects the endpoint weights with the unrestricted splits defining the channels. The next lemma bounds the cost of removing the regularity indicators inside the integrated test; after that removal, the endpoint averages are the unrestricted ones defining the channels.
Lemma 8.1 (Uniform removal of cutoffs). Let k=i+j be an allowed pair with j>0, and let \lvert g\rvert,\lvert h\rvert\le1. Replacing the coefficient and remaining-site regularity restrictions in \E[\mathcal L_{ik}g(S_i)h(S_k)] by no restrictions, while keeping the scalar k_B, incurs an absolute error at most
Here r_B may depend on the fixed regularity parameters and on C_*, but the constant C is independent of C_*, \eta, and C_6. The pairwise gcd restrictions may then be removed at an additional error O(B^{-998}). The resulting integral is
The sum is over positive integers a,b,c.
Proof. Applying the subset identity above at both endpoints in (5.8) turns their subset sums into fair-split expectations, still with regularity indicators attached to the selected and unselected sets, and changes the coefficient k_B/B into k_BB. The remaining coefficient is c=(a-b)/j, and its weight is A_0(c) times its regularity indicator.
All weights other than g,h are nonnegative. We may therefore bound the cost of removing an indicator by putting \lvert g\rvert,\lvert h\rvert\le1 and summing the corresponding positive mass. On the support under consideration, c\asymp X, a,b\asymp TX, and 0.9B\le\log X\le2.2B. There are O(B) dyadic choices of X. Formula (3.5) bounds the split-product probabilities by
Consequently the untruncated mass in one such box is at most
by (3.8), since ab\asymp T^2X^2. If any one of the three coefficients is nonregular, (3.11) gives the same bound with the additional factor r_B+e^{-c_3C_*}. Summing over the boxes proves the required estimate for coefficient failures.
It remains to treat the two unselected endpoint sets. At a given prime p, the probabilities of the three possibilities “selected”, “unselected”, and “absent” are respectively 1/(2p),1/(2p),1-1/p. Conditional on the selected product being a, the unselected indicators at primes not dividing a are therefore independent with probabilities
At primes dividing a they are zero. The same statement holds for b, independently at the other site. Each selected coefficient on our support has log size O(B), and all its prime factors exceed P_0. In particular, the reciprocal sum of its prime factors is O(B/P_0). The uniform cutoff probability estimate established after (3.11) thus bounds either unselected-set failure by r_B+O(e^{-c_3C_*}), uniformly in the chosen coefficients. Multiplying by the preceding positive mass bound and summing the boxes proves (8.1). This argument uses (3.8) and (3.11) for 1\le j\le T; it has made no use of j\ge\eta T or of the block length M. This proves the asserted independence of its constant.
Finally, if one of (a,b),(a,c),(b,c) exceeds one, a prime dividing both a and b must occur. Indeed a-b=jc, and every prime factor of a coefficient is greater than P_0>j. The split products at the two sites are independent, so the probability of a common selected prime is at most
For a fixed pair of selected products there is at most one value of c, and the remaining positive integrand is at most C B\sup_c A_0(c). Since \sup A_0\le(\log P_0)R^{1/2}=B^{1/2+o(1)}, the resulting error is O(B^{3/2+o(1)}/P_0). After removal of these restrictions, the fair splits and independence of the two sites give (8.2) exactly.
8.2 Fourier detection and the discarded arcs
The support of (8.2) already predicts the structure of its real-variable comparison. For a nonzero term put
The exact relation a-b=jc gives
Since u_1,u_2 lie in a fixed compact subinterval of (1,2), the two log coordinates satisfy 0<x-y\ll B^{-1}. We will enforce the discrete relation by additive Fourier orthogonality. This places the c sum in a factor to which the arithmetic estimates apply, while the two signed endpoint sums are controlled by their mass and L^2 bounds. For the surviving small denominators, the channel estimates allow us to average the residue dependence of the endpoint tests with a uniform error, leaving an explicit finite residue sum. Fourier inversion will then give an integral on the narrow logarithmic band, where the coarse channel approximation produces the feature products described above.
We first analyze (8.2) in a single smooth dyadic box. Choose a smooth compactly supported dyadic partition of unity on (0,\infty) for the variable c, and write X=2^m, N_X=TX. A box has c/X in a fixed compact subinterval of (0,\infty). On the support of \Psi_s, both a/N_X and b/N_X are also in fixed positive compact intervals. The smooth weight in the three variables
has all fixed-order derivatives bounded uniformly in m,B,s. This includes \rho_0((\log X+\log(c/X))/B), whose differentiated log-scale factors only improve the bound.
Extend this weight smoothly inside a larger fixed cube, expand the extension in a periodic Fourier series, and multiply each coordinate factor by a fixed smooth compact cutoff equal to one on the original support. We obtain a sum of separated products
More precisely, if \boldsymbol\nu\in\Z^3 indexes the Fourier terms, their scalar coefficients are O_A((1+|\boldsymbol\nu|)^{-A}) for every fixed A, uniformly in the boxes and in s. The fixed-order smooth norms of the factors grow at most polynomially in |\boldsymbol\nu|. All estimates below have only finitely many such smooth-norm losses; choosing A larger than those losses plus four makes every Fourier sum absolutely convergent. When a bound is summed over boxes, we use the uniform coefficient bound at each fixed \boldsymbol\nu. It therefore suffices to write the calculation for one separated term.
For that term set
Additive orthogonality expresses its contribution as
The elementary product formula and Mertens’ estimate give
uniformly in the truncation constant. By (3.5), (3.6), and Parseval,
The first-moment part of (3.6) also gives
The implicit constants here and below include the specified smooth norms of the separated factors.
On the circle of j\alpha\pmod1, take major arcs of radius B^{13}/X about the reduced fractions u/q with q\le B^{12}. They are disjoint for large B: the distance between distinct such fractions is at least B^{-24}, whereas X is exponential in B. On the complement we have
Here are the details of the imported estimate and its application. The Montgomery–Vaughan bound [20, Corollary 1] states that a multiplicative function f satisfying \lvert f(p)\rvert\le1 for every prime p and \sum_{n\le Z}|f(n)|^2\le Z for every Z\ge1 obeys
whenever \lvert\theta-u'/q'\rvert\le1/(q')^2, (u',q')=1, and 2\le R'\le q'\le Y/R'. Apply Dirichlet approximation with denominator limit \lfloor X/B^{12}\rfloor. If the resulting denominator is at most B^{12}, the approximation error is at most 2B^{12}/X<B^{13}/X, so the point is on a major arc. Off the major arcs we consequently have
For every Y\asymp X arising in partial summation, these inequalities permit R'=B^{10}. The function f(n)=\mu_{\rm Mob}^2(n)2^{-\omega(n)}\ind_{\{n\ {\rm rough}\}} is multiplicative and 1-bounded, so it satisfies the theorem’s hypotheses. Smooth partial summation and restoration of the factor
give (8.5).
For later reference, if a discarded region satisfies \lvert S_3\rvert\ll XB^{-a+o(1)}, its contribution in one box is at most
by Cauchy–Schwarz and (8.3). Summing over the O(B) boxes gives a total minor-arc error of
On a major arc, apply (3.2) to S_3. When q>B^{0.4}, its main term is at most X/\varphi(q)\ll XB^{-0.4+o(1)}, uniformly along the arc. Formula (8.6) shows that these arcs cost B^{-0.15+o(1)}/T in total. The error O(XB^{-50}) in (3.2), on all the major arcs together, costs at most B^{-49.75+o(1)}/T. All three errors are uniform in the endpoint tests and are o(1/T).
Put Q=B^{0.4}. The remaining arcs for \alpha have the following exact parametrization:
For each reduced fraction on the j\alpha circle there are exactly j lifts in this list. In particular the parametrization neither omits nor repeats an arc. Define
These transforms are uniformly Schwartz, with bounds controlled by fixed smooth norms. The main term from (3.2) contains the factor X, while d\alpha=d\xi/(jX). The resulting box expression is therefore
In this formula the integration has been extended from [-B^{13},B^{13}] to \R. To justify it, use (8.4), the bound of j\varphi(q) for the number of lifts at denominator q, and a Schwartz bound of any sufficiently large fixed order. The number of boxes and the total arc count are polynomial in B, so the tails give o(1/T) after all sums. Notice also that d\le TQ\le B^{0.72}<B, as required for the channel estimates.
8.3 Fine histograms and residue averaging
The discarded arcs already have negligible total contribution. The remaining major arcs carry a logarithmic coordinate and a unit residue at each endpoint. We next use the channel bounds to retain the former while averaging the latter, uniformly for the endpoint tests.
We replace the split-product measures in (8.7) by the fine log and residue histograms of (7.1). For instance, the replacement for its first sum is
The residue phases have not been approximated. We give the norm estimate which controls this step, its denominator sum, and the subsequent residue projection.
Let I_X\subset I be an enlarged log window about \log N_X/B, of length O(1/B), which contains all fine cells meeting the support of the factors in a box. These windows have bounded overlap as X ranges over its dyadic values, because successive centers are spaced by (\log2)/B. They lie in the interior of I for large B. If F is supported in I_X and bounded, finite Fourier Parseval on \Z/d\Z, with the residue vector extended by zero off the units, gives
Indeed the exact finite Fourier identity, before applying Cauchy–Schwarz to the integrals, is
Here and throughout, the residue component of the L^2 norm uses uniform probability on \mathcal R_d.
For clarity, the histogram replacement can be estimated even when the signed masses \gamma_g have no regularity whatsoever. For a fine cell J and a unit residue r, the definition (7.1) says exactly that
For F(x)=w_1(e^{Bx}/N_X)e(\xi e^{Bx}/(jX)), differentiation on the relevant enlarged window gives
We used e^{Bx}\asymp TX and j\ge\eta T. Thus the oscillation of F on a fine cell is at most
After taking the factor 1/\varphi(d) outside as in (8.8), the residue vector of the replacement error has absolute value at residue r at most
This follows by subtracting the cell average of F from its value at the actual split product and using \lvert h\rvert\le1. Positivity of the measure for U_d1 is the only pointwise information used. Formula (8.9) therefore bounds the squared sum of this error over h' by
The actual, unreplaced sum has the same type of estimate without a_B, by bounding its residue vector with \|F\|_\infty\int_{I_X}U_d1. The replaced sum has (8.9) directly with V=U_dh.
We apply these estimates to the difference of the two products in (8.7), replacing one factor at a time. Cauchy–Schwarz over h' is valid even though the sum is restricted by (h',q)=1, since extending either squared sum to all residues increases it. Afterwards Cauchy–Schwarz over the boxes and bounded overlap of I_X bound the sum of products of local norms by the product of global norms. These global norms are bounded by (7.2). Finally the Schwartz moments absorb the factors 1+|\xi|, as well as the polynomial smooth losses in the separated expansion. Since |I_X|\ll1/B, this proves that at a fixed q the total histogram error, including all boxes, is at most
In particular, the number O(B) of boxes has not introduced an extra factor of B: the local window length cancels the B in (8.7), and the remaining local norms are summed by bounded overlap.
We record explicitly a bound for the denominator sum. The elementary inequality
and partial summation imply
For completeness, to verify the required mean-value input write (n/\varphi(n))^2=\sum_{d\mid n}b(d), where b is supported on squarefree integers and
All these coefficients are nonnegative, and
Hence \sum_{q\le Q}(q/\varphi(q))^2\ll Q, which after partial summation gives (8.11). Since j/\varphi(j)=B^{o(1)} uniformly for j\le T and B\delta_B\asymp B^{-1/10}, summing (8.10) gives o(1/T), uniformly on the allowed lag range.
We now replace U_dh,U_dg in the histogram expression by their residue averages u_h,u_g. Expand the difference of products one factor at a time and repeat (8.9). The only new input is
from (7.2), uniformly in d\le B and the bounded tests. It follows that the error is bounded by
This establishes the residue projection for arbitrary bounded single-site tests, rather than just for the constant test.
8.4 The exact residue factor
After the channel projection, the endpoint tests no longer depend on a residue coordinate. The remaining finite residue sum can therefore be computed exactly; it is the arithmetic factor governing the allowed lags.
After residue averaging, the unit phase average in (8.8) is c_d(h')/\varphi(d), where
is the Ramanujan sum. The second endpoint contributes its complex conjugate phase average. Since the coefficient of a nonsquarefree q in (8.7) is zero, only squarefree q matter. For such q the exact identity is
Here is a direct proof that also covers nonsquarefree j. If p\mid(j,q), the modulus jq is divisible by p^2, while (h',q)=1 forces p\nmid h'. For every a\ge2,
Chinese remaindering therefore makes the whole Ramanujan sum zero. If (j,q)=1, the Ramanujan sums split over the two coprime moduli. At the squarefree modulus q, a unit frequency has c_q(h')=\mu_{\rm Mob}(q), of absolute value one. At modulus j, orthogonality gives
The numerator on the left of (8.12) is thus j\varphi(j)\varphi(q), and division by \varphi(jq)^2=\varphi(j)^2\varphi(q)^2 proves the identity.
Combining (8.12) with the factor \mu_{\rm Mob}(q)/\varphi(q) in (8.7) yields the singular series
The series is absolutely convergent: for every fixed \epsilon>0, 1/\varphi(q)\ll_\epsilon q^{-1+\epsilon}, so
This tail bound is independent of j. Also
The series vanishes when j is odd, consistently with the parity obstruction in a-b=jc for rough coefficients.
After the residue projection, the archimedean integrals in (8.7) no longer depend on q. The total over boxes of their absolute values, before the factor B/j, is O(1/B): apply Cauchy–Schwarz on their log windows, then use bounded overlap and \|u_g\|_2,\|u_h\|_2\ll1. The Schwartz integrations and smooth expansions have the same summability as before. It follows that replacing the sum q\le Q by (8.13) costs at most
In particular this is a uniform vanishing multiple of (j/\varphi(j))/j.
8.5 Archimedean inversion and coarse features
For one separated box, the phase remaining in the product of archimedean integrals is
Fourier inversion in \xi therefore evaluates w_3(z')m_B(\log(Xz')/B) at z'=(e^{Bx}-e^{By})/(jX). The inversion introduces no further Jacobian: its integration variable is \xi. Recombining the separated factors and the dyadic partition gives
Weights are interpreted as zero off their positive domains and supports. The inversions and rearrangements are justified for u_g,u_h\in L^2(I) by the bounded log windows, the Schwartz transforms, and the absolutely summable smooth expansion, with the absolute-product bound just used for (8.14).
We spell out the support properties needed to approximate (8.15). There is a compact interval [a_0,b_0]\subset(1,2) containing the support of \psi. Write v=B(x-y). If the \Psi_s factor is nonzero, its two arguments u_1,u_2 lie in [a_0,b_0], with
For \eta\le\lambda\le1, this implies
If these inequalities have no solution for a particular \lambda, the weight is simply zero. On this support,
The functions m_B\rho_0, extended by zero beyond a fixed compact interval inside (0,4), converge uniformly to m\rho_0, with uniformly bounded derivatives. It follows that
uniformly wherever the integrand can be nonzero.
To quantify its effect for arbitrary tests, consider the integral operator with nonnegative kernel
Its row and column integrals are at most C, so Schur’s inequality gives a uniform L^2 operator bound. Multiplication by the bounded smooth weights preserves that bound. Since \|u_g\|_2,\|u_h\|_2\ll1, the replacement of m_B(z)\rho_0(z) in (8.15) costs o_\eta(1)\mathfrak S(j)/j.
Given \epsilon_1>0, choose the fixed coarse partition in (7.3), and write u_g^{\rm c}=P_{m_1}u_g, u_h^{\rm c}=P_{m_1}u_h. The same operator bound and the contraction property of P_{m_1} show that replacing the two endpoint functions by u_g^{\rm c},u_h^{\rm c} costs at most
This constant does not grow with the chosen coarse partition; the errors tending to zero may of course depend on that fixed partition. Its coarse functions satisfy
By (8.16), x and y belong to the same coarse cell except when y is within C/B of one of the finitely many cell boundaries. The area of these exceptional pairs is O_{m_1}(B^{-2}): the total possible length for y is O_{m_1}(B^{-1}), and for each such y the possible length for x is O(B^{-1}). Thus replacing u_h^{\rm c}(x) by u_h^{\rm c}(y) costs O_{\eta,m_1}(B^{-1})\mathfrak S(j)/j. The support of m(y)\rho_0(y) is a fixed positive distance from the boundary of I, so there is no further boundary contribution from the condition x\in I for large B.
Recall the coarse features from Corollary 7.4, and define their deterministic coefficients by
These are nonnegative, V_l(S)\le |I_l|^{-1}, and h_l\ge0. Since the fine partition refines the coarse partition, averaging (7.1) over a coarse cell gives the exact identity
After the preceding replacements in (8.15), substitute x=y+v/B. The factor dx=dv/B cancels its prefactor B, and 1/j=(1/T)(1/\lambda). The resulting integral tests are therefore precisely those of the following site matrix:
The matrix is zero off the allowed pairs. Formula (8.17) defines it for both signs of j; it is symmetric because its displayed dependence on the endpoints is symmetric. For positive j, independence of the endpoint types turns its integral test against g,h into the product of the two expectations just displayed. The case of negative j follows by exchanging the endpoints.
The function w is nonnegative and smooth, with all fixed-order derivatives bounded on the relevant compact s-range and \eta\le\lambda\le1. There is in fact an expression giving bounds independent of \eta. In (8.17) put u=\lambda/(e^v-1). Then dv=-\lambda\,du/(u(u+\lambda)), and hence
The factors \psi(u)\psi(u+\lambda) restrict the integration to a fixed compact subset of u>0. Consequently this formula extends w smoothly to 0\le\lambda\le1, with uniformly bounded derivatives there, and gives zero when \lambda>b_0-a_0. Differentiation under the integral is valid because its denominators are bounded away from zero on that fixed support.
8.6 Uniform integral cut comparison and row bounds
The preceding calculation has produced the finite-feature matrix \mathcal M. We now collect its approximation error in the same block normalization as the original energy and record the row bounds needed when the endpoint types are sampled.
Proposition 8.2 (Integral comparison). For the matrix \mathcal M in (8.17), put \mathcal E_{ik}=\mathcal L_{ik}-\mathcal M_{ik}, with all three matrices zero on nonpairs. Given \epsilon_1>0, choose the coarse partition as in (7.3). Then
The o(1) is uniform in s and in all the indicated tests. The coefficient of e^{-c_3C_*} is independent of \eta, C_6, and C_*. In addition, for every realization of the site types,
Proof. Every estimate above was uniform in a pair of tests with absolute value at most one. Apart from (8.1), the pre-projection arc errors are uniform o(1/T). The histogram and residue projection errors have the explicit common upper bound
The series tail is bounded by (8.14), and the archimedean and coarse replacements have total error
All these bounds hold separately for every allowed edge. They thus remain valid if the endpoint tests differ from edge to edge, and in particular for the collection of tests in (8.19).
For a fixed positive lag there are at most M ordered pairs with that lag; including the negative lag at most doubles this number. Division by M therefore reduces their total error to at most twice the sum of the edge error over \eta T\le j\le T. The first-moment bound for \Sigma gives
Consequently the sum of (8.1) is O(r_B+e^{-c_3C_*}), with a constant independent of \eta,C_6,C_*. A uniform o(1/T) error sums to o(1). For the other errors use the bounded mean of j/\varphi(j) and
Since \log(2Q)(B\delta_B+B^{-c_7})\to0, the denominator sum contributes o(1). Absolute convergence makes the series tail tend to zero as well. Finally \mathfrak S(j)\le j/\varphi(j) controls the archimedean and coarse errors, giving the stated C_\eta\epsilon_1+o(1). There is no factor of C_6, because the count of pairs for each lag has already been divided by M. This proves (8.19).
For the deterministic row estimates, boundedness of k_B, w, and the finitely many features gives the pointwise bound
on allowed pairs. Each row has at most two entries for each positive lag. The first and second powers of j/\varphi(j) have bounded means. For the second power this was proved before (8.11), and the first follows by Cauchy–Schwarz. Summing the displayed pointwise bound and its square over 1\le j\le T proves (8.20), uniformly in every collection of site types and in the block length.
9 Sampling the integral cut comparison
The comparison in (8.19) allows arbitrary bounded functions at each single site. To use it against the labels in (5.4), we must also allow the testing signs to depend on the entire sampled matrix. We do this by approximating an optimizing row-sign vector using a small set of columns, and then applying concentration simultaneously to the resulting finite family of optimizations.
The small-column approximation is related to the sampling argument of Alon, Fernández de la Vega, Kannan, and Karpinski [1, Lemma 3] and to the proof of Borgs et al. [2, Theorem 4.6]. Their arguments approximate optimizing cuts by a small sample and then control a finite family of tests. Here the kernels depend on B and on position, and are controlled by degree bounds and integrated row-second-moment bounds. We therefore prove the required sampling transfer directly rather than invoking those results as a black box.
Throughout this section the regularity parameters, C_*, \eta, C_6, \epsilon_1, and the coarse partition are fixed. In particular, T=\lfloor B^{0.32}\rfloor and M=\lceil C_6T\rceil\asymp B^{0.32}. All limits and o(1) terms in the probabilistic argument refer to B\to\infty with these parameters fixed. We work at one value of s in the fixed compact range of the smooth weights. Every bound below is uniform in that value of s; no simultaneous event over all s will be needed.
Let \mathbf S=(S_1,\ldots,S_M) have the independent site law from Section 5. Write
Here the fixed constants in E_0 are large enough for (8.19). As established there, the coefficient C of e^{-c_3C_*} can be chosen independently of \eta and C_6. The matrices are real and symmetric, and are zero on the diagonal and on all nonallowed pairs. We retain the normalization
Proposition 9.1 (Sampling the type-kernel comparison). For every fixed \epsilon_2>0,
uniformly for s in the fixed compact range.
We first record the degree and integrability estimates required in the proof. Use the nonnegative symmetric envelope
Dependence on the endpoint types and on s is suppressed when no confusion is possible. By the every-type bound (5.9) and the deterministic absolute row bounds for (8.17), there is a constant C_0 such that
By (6.1) and the squared-row bounds following (8.19), there is a constant C_1 such that
Indeed (\mathcal L_{ik}+|\mathcal M_{ik}|)^2 \le2\mathcal L_{ik}^2+2\mathcal M_{ik}^2, and 1/T=O(B^{-0.32}). These squared-row bounds are integrated over the row type; no uniform conditional second-moment assertion is being made.
Lemma 9.2 (A common degree event and uniform integrability). There is a fixed K>0 such that, on an event \mathcal G_B of probability 1-O(B^{-0.01})-O(B^{-0.03}),
The event may also be required to satisfy \max_i\sum_k\mathcal H_{ik}\le K B^{0.07}. Moreover, the normalized total absolute mass
has bounded second moment, uniformly in B and s.
Proof. Put D_i=\sum_k\mathcal H_{ik} and d_B=K B^{0.07}, where K is any fixed sufficiently large constant. Conditional on S_i, the summands of D_i are independent, since each off-diagonal summand depends on one other independent site. Consequently
For sufficiently large B, d_B\ge2C_0. Conditional Chebyshev followed by averaging the row type gives
Thus the event
has complement of probability O(Mq_B/d_B^2)=O(B^{-0.03}). Markov’s inequality gives
Take
This implies (9.2). Finally, Jensen’s inequality across rows gives
In particular, for any events \mathcal B_B with probabilities tending to zero uniformly in s, \E[A_B\ind_{\mathcal B_B}]=o(1) by Cauchy–Schwarz.
The same degree estimate applies to the graph induced by any fixed subset of indices: deleting terms decreases both its conditional expected degrees and its integrated squared-row sums. In particular, the probability of a degree exceeding d_B is still O(B^{-0.03}) after a union over its at most M rows. This remains true conditional on the types at indices outside the subset, since the remaining types retain their original independent laws.
Lemma 9.3 (Approximation by a small set of columns). Put m_2=\lfloor M B^{-0.18}\rfloor. On \mathcal G_B there are a subset J'\subset\{1,\ldots,M\} of size m_2 and signs (\delta_j)_{j\in J'} such that, with
and assigning the sign +1 at zero for all sign choices in this section,
The constants are independent of the realized matrix on \mathcal G_B.
Proof. Fix the realized matrix. Choose column signs \delta_k attaining the cut norm and choose the best-response row signs, so the unnormalized maximum is the positive quantity \sum_i|r_i|, where r_i=\sum_k\mathcal E_{ik}\delta_k. For this deterministic matrix only, sample a uniform subset J' of m_2 columns and form the unbiased estimate
The variance formula for sampling without replacement yields
For real numbers r and \widehat r, |r|-r\sgn(\widehat r)\le2|r-\widehat r|. Applying this inequality and then Cauchy–Schwarz across rows, the expected loss in the unnormalized bilinear sum is at most
Here m_2\asymp M B^{-0.18} for large B. Hence at least one subset has this loss bound, with \sgn(\widehat r_i)=\widetilde g_i. Its signs on J' are the restrictions of the chosen optimizing column signs.
Deleting every ordered pair with an endpoint in J' changes any such bilinear sum in absolute value by at most 2m_2d_B, using symmetry and the degree event. After deletion, maximizing the column signs gives exactly \sum_{k\in R'}|\sum_{i\in R'}\mathcal E_{ik}\widetilde g_i|. Since m_2d_B/M=O(B^{-0.11}), the claim follows.
Lemma 9.4 (Uniform mean after fixing a column set). Fix a deterministic subset J' of size m_2 and a deterministic assignment \sigma\in\{-1,1\}^{J'}. Condition on its site types \mathbf S_{J'}=\mathbf t. For i\in R', define the fixed single-site function
Then, writing
we have \E[Z_{J',\sigma,\mathbf t}\mid\mathbf S_{J'}=\mathbf t] \le E_0+o(1), uniformly in J', \sigma, \mathbf t, and s.
Proof. Only the types in the deterministic set J' have been conditioned on. In particular, no event describing which signs an optimizer would choose has been imposed. The types in R' remain independent with their usual laws, and |g_i|\le1.
For k\in R' and a possible value v of S_k, put
Choose h_k(v)=\sgn(a_k(v)), and set both families of tests equal to zero on removed indices. Equation (8.19), which is uniform over all bounded single-site tests, gives
This application is valid for every fixed value of \mathbf t, however the resulting functions g_i depend on that value.
Conditional on S_k, the centered terms
are independent. The diagonal contributes zero. Conditional variance followed by Cauchy–Schwarz therefore gives
Symmetry supplies the squared-column bound from the squared-row bound. Averaging this estimate over k costs at most q_B^{1/2}=O(B^{-0.105}). This proves the asserted mean bound, including its uniformity in the conditioned choice.
Proof of Proposition 9.1. The skeleton lemma reduces the adaptive cut norm to a finite family of optimizations, each with conditional mean at most E_0+o(1). The remaining step is a concentration estimate strong enough to hold for the entire family. The common degree event will be excluded only once. We prove concentration for each of the deterministic subset/sign assignments in Lemma 9.4, and then take a union over those assignments. Fix such an assignment and condition on \mathbf S_{J'}=\mathbf t. Abbreviate its random quantity by Z. Let \mathcal G_{R'} be the set of configurations of the remaining site types satisfying
The observation after Lemma 9.2 shows that
uniformly in the conditioning and assignment.
We next verify a Lipschitz bound between any two configurations \mathbf u,\mathbf v\in\mathcal G_{R'}, rather than only between good configurations differing in one coordinate. Let A=\{i\in R':u_i\ne v_i\}. The row functions g_i have already been fixed by \mathbf t and \sigma. Thus a term \mathcal E_{ik}(u_i,u_k)g_i(u_i) can change only if i or k belongs to A. The reverse triangle inequality for each column sum gives
The last inequality uses both endpoint degree bounds and symmetry. It also includes the change of g_i when i\in A. No connecting path of good configurations is required.
Choose a fixed L'>E_0+2+\epsilon_2. On \mathcal G_{R'} the function f=\min(Z,L') is nonnegative and Lipschitz for the site Hamming distance d_H, with constant c_B=4d_B/M. For sufficiently large B the good set is nonempty. We use the McShane extension [19] in its infimum form [3, Section 3, Equation (3.2)], followed by clamping:
The site spaces are finite for every B, so the formula is measurable. The infimum defines a c_B-Lipschitz function by the triangle inequality, and its restriction to the good set is f: the Lipschitz inequality for f gives the lower bound, and taking \mathbf v=\mathbf u gives the upper bound. Clamping preserves the Lipschitz bound. Hence 0\le\widetilde Z\le L' everywhere and \widetilde Z=\min(Z,L') on \mathcal G_{R'}. By Lemma 9.4,
again uniformly in every fixed choice.
Changing any one of the independent remaining site types changes \widetilde Z by at most c_B. McDiarmid’s bounded-differences inequality [18] therefore gives, for every a>0,
Taking a=\epsilon_2/4 and using the uniform mean bound shows that, for large B,
On \mathcal G_{R'}, the event Z>E_0+\epsilon_2/2 is equivalent to this event for \widetilde Z, since the threshold is strictly below L'.
There are at most
deterministic subset/sign assignments. For each assignment, integrate the last conditional tail bound over its subset types. We may then union-bound the extension tails, because
The original full-sample event \Omega_{\rm deg} implies \mathcal G_{R'} for every subset J' simultaneously, by nonnegativity of the envelope. Consequently
Only the exponential extension tails have been union-bounded; the probability of \Omega_{\rm deg}^c is counted once.
With probability 1-o(1), the squared-mass event also holds, and Lemma 9.3 now bounds the fully adaptive cut norm by E_0+\epsilon_2/2+O(B^{-0.01})+O(B^{-0.11}). On the exceptional event use \|\mathcal E\|_\square\le A_B. Lemma 9.2 makes its expected contribution o(1). This proves (9.1). All probabilities and errors used here were uniform for each fixed s in the compact range, which proves the stated uniformity without constructing a simultaneous event over s.
The deterministic row estimate (8.20) gives
uniformly in the site types and in s. Thus \mathcal M satisfies the O(B^{10}) total-mass hypothesis of the independent-root comparison.
Finally, combine (9.1) with the independent-site comparison (5.10). For the actual sets S_i(n)=\{p\in\mathcal P:p\mid n+i\} and fixed B, the upper limit as x\to\infty of the absolute error in replacing the kernel in (5.4) by \mathcal M_{ik}(S_i(n),S_k(n);n/(Tx)) is at most
Here x tends along the fixed bad subsequence, and the o(1) tends to zero as B\to\infty after this inner upper limit. The constant C_{\rm lab} depends only on the fixed label bound and the compact s-range. Indeed bounded complex label energies are controlled by a fixed multiple of the real cut norm. For each fixed B, the error norm is a finite maximum of finite-residue functions continuous in s (piecewise continuity would also suffice), so ordinary scale counting gives its Haar expectation integrated over s, as explained after (5.4). The uniform expectation bound above can then be integrated over that fixed compact interval. This uses no independence between the actual labels and site types, and all matrices retain zero entries on nonallowed pairs.
10 Vanishing of the main energy
The main kernel in (8.17) has finitely many bounded site features. We first approximate these features by multiplicative weights and the lag factor by a function with a fixed period. Subdividing the position block then reduces its energy to products of the short averages in Lemma 2.3. In the vanishing argument, the regularity parameters, C_*, \eta, C_6, and the coarse partition are fixed; further approximation parameters are chosen before the limits. We take x\to\infty along the bad subsequence fixed in Section 2, and only then B\to\infty.
Choose a compact interval \mathcal I_s=[s_0,s_1]\subset(0,\infty) containing the supports in s of all the kernels under consideration. It depends only on the fixed smooth functions: the support conditions \psi(u_1)\psi(u_2)\ne0 and \phi(s/u_1)\phi(s/u_2)\ne0 put s in such a fixed interval. For the actual site sets
write the main-kernel energy as
The summands are zero away from the original smooth supports. In particular, the choice of the enclosing interval introduces no new term.
Lemma 10.1 (Approximation of the site features). Fix the coarse partition I=\bigcup_{l=1}^{m_1}I_l used in (8.17). For every \zeta>0 there are real polynomials
independent of B, such that the functions
satisfy, for all sufficiently large B,
Here the norm uses the independent site law with inclusion probabilities 1/p. For 0<\zeta\le1, the approximants can be chosen with a common bound depending only on the fixed coarse partition. At actual integer sites they are the fixed finite combinations
where G_{B,v} is the function in (2.11) with P_B=\mathcal P.
Proof. Write x_b=(\log b)/B for the normalized logarithm of the fair split product b, and put q_l^0(y)=\ind_{I_l}(y)/|I_l| for y\ge0. The endpoints of the coarse cells lie in [1/2,3], where (3.3) bounds the marginal split-product densities uniformly for large B. Choose small endpoint neighborhoods, still in a fixed compact subinterval of (0,3.2), and replace q_l^0 by a continuous compactly supported function q_l. We may arrange 0\le q_l\le1/|I_l|, with equality to q_l^0 outside these neighborhoods. By (3.3), their \nu_{1/2} mass is at most a constant times their total length plus O(B^{-80}). Consequently the neighborhoods can be fixed so that
is as small as desired, simultaneously for the finitely many cells.
The function t\mapsto q_l(-\log t) on (0,1], assigned value zero at t=0, is continuous on [0,1]. Indeed q_l is zero for all sufficiently large arguments. Uniform polynomial approximation on [0,1] therefore gives a real polynomial p_l for which p_l(e^{-y}) approximates q_l(y) uniformly for every y\ge0. Both this approximation and the preceding endpoint smoothing can be chosen so that
for all sufficiently large B. Taking the uniform polynomial error at most one also ensures \sup_{0\le t\le1}|p_l(t)|\le1/|I_l|+1.
Conditional on a site set S, fair splitting gives
The second identity follows by making the fair split choices separately for each prime. Conditional expectation is a contraction in L^2, which proves the asserted error bound and the uniform bound on the approximants. The last identity applies to the distinct primes dividing n+i, irrespective of their multiplicities, and hence gives exactly G_{B,v}(n+i) at the integer sites.
We spell out how the feature error is used against the labels. For fixed B, any function of S_i(n) is a function of finitely many residues of n+i. Unweighted progression counting gives, for r=1,2,
There are only finitely many i at fixed B; neither a bound on the size of the residue modulus nor uniformity with respect to growing B is required for this inner limit.
The singular series in (8.13) is nonnegative and at most j/\varphi(j). Its ordinary mean is bounded. Thus the lag majorant has deterministic row bounds
For completeness, the identity
and the convergence of \sum_d\mu_{\mathrm{Mob}}^2(d)/(d\varphi(d)) give this bound by summing the divisor expansion up to T. Since |F_x|\le2, the features and their approximants are bounded, and k_B, w and the finitely many h_l are bounded for the present fixed parameters, replacing both features in each term of (10.1) costs at most C\zeta in iterated upper limit. Indeed
and (10.3) reduces the sum to the single-site L^1 errors in (10.2). This uses no independence between either feature error and the labels or the other endpoint.
Lemma 10.2 (Periodic approximation of the lag factor). For a fixed prime cutoff P_1\ge2, define on all integers j
This is a bounded nonnegative function of period D=\prod_{p\le P_1}p. Moreover,
with the supremum taken over positive integers T.
Proof. Write
The omitted nondividing-prime factors form a product of numbers in (0,1]. Since P_1\ge2, its difference from one is at most
uniformly in j. All the retained nondividing-prime factors are in [0,1], including the possible zero factor at p=2. Consequently
The positive divisor expansion gives
Its mean up to T is bounded by
The unrestricted positive series equals \prod_p(1+1/(p(p-1)))<\infty, so this tail tends to zero. The same expansion bounds the mean of a(j) by that product, uniformly in T. The required conclusion follows.
Proposition 10.3 (Vanishing of the main energy). With C_*, \eta, C_6, and the coarse partition fixed as above,
Proof. Let \gamma>0 be arbitrary. First choose the approximants in Lemma 10.1 with sufficiently small \zeta that the feature replacement has iterated upper-limit error at most \gamma/3. Their degrees and coefficients are now fixed, and the approximants have the stated bounds depending only on the fixed coarse partition. Next choose a fixed P_1 by Lemma 10.2. Replacing \mathfrak S(|k-i|) by \mathfrak S_{P_1}(k-i) in the energy costs at most \gamma/3 in upper limit. To check the normalization, the absolute error is bounded by a fixed constant times
The label and origin bounds have been absorbed in that fixed constant.
Choose a fixed 0<\delta<\eta/4, to be made small after P_1 has been fixed. Partition \{1,\ldots,M\} into a fixed number R_0 of consecutive blocks J_a, 1\le a\le R_0, of lengths L_a differing by at most one. Choosing R_0 sufficiently large in terms of \delta,C_6, for all sufficiently large B we have
with a positive fixed lower constant. In particular all these lengths tend to infinity.
Call an ordered block pair fully allowed when every (i,k)\in J_a\times J_b satisfies \eta T\le|k-i|\le T. Discard any block pair containing both an allowed and a nonallowed pair of positions. The values of |k-i| on a block pair vary by at most 2\delta T. Thus each discarded allowed pair has lag within 2\delta T of \eta T or T. For each row there are only O(\delta T+1) such positions. The factors now present, including the periodic lag factor, are bounded for the fixed P_1 and coarse partition. With the normalization 1/(MT), this discarding costs O(\delta)+O(1/T), with a constant allowed to depend on these already fixed parameters.
Choose a representative position i_a\in J_a for every block, and for every fully allowed block pair put \lambda_{ab}=|i_b-i_a|/T\in[\eta,1]. Smoothness of w on the fixed compact s-range and on \eta\le\lambda\le1 gives
Replacing the weight by this representative value therefore has another O(\delta) cost. We fix \delta sufficiently small that the two block errors together have upper limit at most \gamma/3. Neither the representatives nor their scaled lags have to converge as B grows; only this uniform bound is used.
It remains to show that the fully factored expression tends to zero. For 0\le r<D and 1\le l\le m_1, define
By the feature identity, this is a fixed finite linear combination of
The lengths L_a tend to infinity and the starting indices are fixed for each B. The modulus D, monomials v, and polynomial coefficients are all fixed before B grows. Lemma 2.3 applies with origins n\in[s_0Tx,s_1Tx], and yields
for every one of the finitely many indices.
Set c_{r,r'}=\mathfrak S_{P_1}(r'-r), using the periodic extension in Lemma 10.2, including at the zero residue. On a block pair, splitting each position by its residue class gives the factored expression
The feature polynomials are real, so the conjugation here matches exactly the conjugation in the original energy. The factors L_aL_b/(MT) are uniformly bounded. The numbers of cells, blocks, and residue classes are fixed, and k_B and the representative smooth weights are uniformly bounded. Cauchy–Schwarz in the origin variable and (10.4) make every term in (10.5) tend to zero in the asserted iterated upper-limit sense. This remains true when the bounded coefficients depend on n/(Tx) or on B.
The original main energy consequently has iterated upper limit at most \gamma in absolute value. Since the approximation parameters were fixed before the limits and \gamma>0 was arbitrary, the proposition follows.
Proof of Proposition 2.2. Suppose mixed decorrelation fails for some fixed J and two fixed phase vectors. Fix the resulting subsequence, the limiting profile W and bump \phi from Section 2, and the smooth functions \rho_0,\psi from Section 4. Choose the regularity grid and tolerances as required for the estimates of Sections 3 and 6. The amplification then supplies the positive constant c_5 in (4.10). This constant is independent of every sufficiently large fixed C_*.
We collect the upper bounds, recording the dependencies needed to choose parameters without a cycle. The diagonal contribution to I_{2,x}/(BT) tends to zero in the prescribed order. Equations (5.1)–(5.4) express the remaining contribution as the block energy, up to errors bounded in iterated upper limit by
Here C_0 can be chosen independently of C_*, \eta and C_6, by the untruncated mean bound (5.3).
The root comparison (5.10) and the sampling bound (9.1) allow replacement of this block kernel by \mathcal M. The resulting upper-limit error is bounded by
The constants C_1,C_2 do not depend on the later choices \eta,C_6 or the coarse partition. Indeed the truncation term in (8.19) has a coefficient independent of the lag range and block length, and converting a real cut-norm bound to an energy of labels of absolute value at most two costs only an absolute factor. For example, splitting each label into its real and imaginary parts gives a factor at most 16. Integrating over \mathcal I_s costs only its fixed length. The finite-residue counting passage and the uniformity in s were established in Sections 5 and 9. The remaining o(1) errors vanish as B\to\infty after the inner x-limit, with all the displayed parameters fixed.
For any such fixed choices, Proposition 10.3 makes the main energy zero in upper limit. Consequently
First choose a sufficiently large fixed C_* so that the first term is less than c_5/10. Next choose a sufficiently small fixed \eta and a sufficiently large fixed C_6 so that the next two terms are each less than c_5/10. Then choose positive fixed \epsilon_1,\epsilon_2 so that their terms are each less than c_5/10, and choose the corresponding coarse partition in (7.3). All feature, periodic and block approximations in Proposition 10.3 are made subsequently with these parameters fixed. Thus (10.6) is strictly smaller than c_5, contradicting the lower bound (4.10).
Finally, the bad subsequence was extracted from an arbitrary sequence of integer scales on which x^{-1}\sum_{1\le n<x}\overline{g_x(n)}F_x(n+1) stays a fixed positive distance from zero. Every inner limit above uses the final subsequence selected for the profile. At each fixed B, all multipliers, residue moduli and shifts are finite, so the argument never requires their invariance or counting estimates while B and x grow simultaneously. The contradiction rules out every original sequence of this kind. Thus the mixed correlation tends to zero along the full sequence of integer scales, for every fixed pair of phase vectors.
11 Marginals, the joint law, and the ordering corollary
Proposition 2.2 separates every pair of bin characters. Finite Fourier inversion therefore separates bin events, including smoothness at rational powers of the counting scale. The factorial-moment limits from Section 2 identify their marginals with the Dickman law. We then obtain the fixed-scale joint law through every real counting endpoint, pass to the moving thresholds in Theorem 1.1, and deduce the comparison corollary from the continuous limiting distribution.
11.1 Finite Fourier inversion
Adding back the centering in Proposition 2.2 gives
Here and throughout this subsection, x runs through positive integers. Indeed, the mean of \overline{g_x(n)} tends to \overline{\mu_g} by Lemma 2.1 and its initial-segment extension. For m\le x, write
Every coordinate lies in \{0,\ldots,J\}: each counted prime factor exceeds x^{1/J}. Thus reduction modulo J+1 is injective on the set of count vectors. Put \zeta_0=\exp(2\pi i/(J+1)). For \boldsymbol r\in\{0,\ldots,J\}^{J-1} and such a count vector \boldsymbol b, the exact identity
expresses each bin event as a finite linear combination of characters. The two phase vectors in (11.1) are independent choices, and complex conjugation simply permutes the available root-of-unity phases. Applying this identity at n and n+1 proves factorization of the limiting expectations of every pair of fixed functions of their count vectors. Both marginal limits exist by Lemma 2.1; the shift of the averaging range changes a bounded marginal average by O(1/x).
If c,d\in(0,1) are rational, choose J so that both are grid points. For m\le x, the condition \Pplus(m)\le x^c is exactly the vanishing of all counts in bins with lower endpoint at least x^c. Hence the joint smoothness event with thresholds x^c,x^d has a limiting density equal to the product of its two marginal limits. The next calculation identifies those limits.
11.2 The Dickman marginal
We recover the classical marginal law, originating with Dickman and developed by Ramaswami and de Bruijn [4, 6, 22], from the factorial moments already computed for the bin counts.
Lemma 11.1 (Dickman marginal). For every fixed c\in(0,1),
The limit is through all real x.
Proof. First suppose that c=k_0/J for integers J\ge2 and 1\le k_0<J. For m\le x, set
Then \Pplus(m)\le x^c exactly when N_{c,x}(m)=0, and 0\le N_{c,x}(m)\le J. For a nonnegative integer z, write (z)_h=z(z-1)\cdots(z-h+1), with (z)_0=1. The finite inclusion–exclusion identity is
For each 0\le h\le J, the falling-factorial multinomial identity gives
Apply the initial-segment form of (2.9) to every term, with r_k=0 for k<k_0. The multinomial coefficient counts the assignments of the h ordered variables to the bins. Summing the resulting simplex integrals therefore joins those bins into (c,1] and gives
For h=0, the empty integral is one, and the left-hand limit is also one. The initial-segment limit used here holds through real x, as does the factorial-moment limit in Section 2.
In this integral put s_i=cv_i. The upper bound on each v_i is then implied by v_1+\cdots+v_h\le1/c, and changing the lower boundary from v_i>1 to v_i\ge1 does not change the integral. Averaging the inclusion–exclusion identity shows that the rational smoothness density is H(1/c), where for u\ge0 we put
The sum is locally finite because I_h(u)=0 when h>u. In particular, 1/c\le J ensures that the sum at u=1/c agrees with the finite inclusion–exclusion sum above. Put I_0(u)=1 for u\ge0.
For h\ge1 and y>z\ge1, symmetry and the identity 1=(v_1+\cdots+v_h)/(v_1+\cdots+v_h) give
To verify this, cancel the last denominator after using symmetry and set t=v_1+\cdots+v_h. The remaining variables satisfy v_1+\cdots+v_{h-1}\le t-1. The same formula holds for h=1. Thus the I_h are continuous, H=1 on [0,1], and
Successive integration on the intervals [k,k+1] uniquely determines a continuous solution from its values on [0,1]. Hence H=\rho, proving (11.2) for rational c.
For an arbitrary real c\in(0,1), choose rational c_-<c<c_+ in (0,1). The smoothness event at x^{c_-} is contained in the event at x^c, which is contained in the event at x^{c_+}. The rational limits bound the lower and upper limits of the middle normalized count by \rho(1/c_-) and \rho(1/c_+). Letting c_-,c_+ approach c and using continuity of \rho at the finite argument 1/c proves (11.2).
The marginal law also supplies the endpoint behavior of the limiting distribution. It gives 0\le\rho(u)\le1 for u>1, and the same bounds hold at u=1 by definition. The delay equation makes \rho nonincreasing on [1,\infty). Its limit at infinity must be zero: if that limit were L>0, integrating \rho'(u)=-\rho(u-1)/u\le-L/u would contradict nonnegativity. Consequently
is a continuous distribution function, including at zero and one, and its probability measure has no atoms.
11.3 Fixed and moving thresholds
Combining the Fourier inversion with Lemma 11.1 gives, for every pair of rational c,d\in(0,1),
We first extend this fixed-scale law to arbitrary real exponents and real counting endpoints. Fix c,d\in(0,1) and rational exponents c_-<c<c_+ and d_-<d<d_+ in (0,1). Given real X, put x=\lfloor X\rfloor+1. Then x/X\to1, the integer ranges n\le X and n<x agree, and for all sufficiently large X,
Thus the normalized count over 1\le n\le X with thresholds X^c,X^d lies between x/X times the two normalized counts in (11.6) at the lower and upper rational exponents. Taking lower and upper limits through real X, then letting the rational exponents approach c,d, proves
The omission of n=1 changes at most one summand. In (11.7), the exponents are fixed and the limit is through all real X.
This also gives the fixed-scale upper-tail independence law discussed by Erdős and Pomerance [7, p. 311]:
For interior exponents this follows by inclusion–exclusion from (11.7) and the two marginal laws. The marginal for n+1 is the one in Lemma 11.1, since shifting its counting range changes only O(1) terms. Replacing either strict comparison in (11.8) by a weak one has the same limit. Indeed, for fixed c>0, equality \Pplus(m)=X^c is impossible unless X^c is a prime p; in that case every such m is divisible by p, giving only O(X^{1-c}+1)=o(X) possibilities for m\le X+1. At exponent zero, the upper-tail condition holds for every m\ge2, and equality can occur only at m=1. At exponent one, an upper-tail condition on m\le X+1 has only O(1) possible integers. These observations give the endpoint cases of (11.8) as well. Its right-hand side is continuous on [0,1]^2 by (11.5).
Proof of Theorem 1.1. Fix a,b\in(0,1) and choose fixed exponents c_-<a<c_+ and d_-<b<d_+ in (0,1). For each fixed \varepsilon\in(0,1), all sufficiently large real X satisfy, uniformly for \varepsilon X\le n\le X,
On this interval, the fixed-scale event at the lower exponents is contained in the moving-threshold event of Theorem 1.1, which is contained in the fixed-scale event at the upper exponents. The discarded initial interval costs at most \varepsilon+O(1/X) in normalized counting. The limit through all real X in (11.7) therefore bounds the lower and upper limits of the desired count by the corresponding products at the lower and upper exponents, with that error. Let \varepsilon\downarrow0, then let the exponents approach a,b. Continuity of D gives the claimed product through all real endpoints, with ordinary, unweighted counting.
11.4 The ordering probability
Proof of Corollary 1.2. For n\ge2, put
The empirical probability law means uniform sampling from 2\le n\le\lfloor X\rfloor; its normalization 1/(\lfloor X\rfloor-1) differs from 1/X by a factor tending to one. Recall the continuous distribution function D from (11.5).
Although 0\le U_n\le1, the second coordinate can slightly exceed one. This overshoot vanishes and does not alter the limiting law: for every n\ge N\ge2,
Consequently the empirical laws are tight and every limiting law is supported on [0,1]^2. More explicitly, clamp V_n to \widetilde V_n=\min(V_n,1). For 0<a,b<1, the joint distribution functions of (U_n,\widetilde V_n) are exactly those of (U_n,V_n), hence converge by Theorem 1.1 to D(a)D(b). These interior rectangles determine the limiting probability law: their masses approach one as a,b\uparrow1, and finite differences give the masses of all interior grid cells. Approximating continuous functions on [0,1]^2 by such grids proves weak convergence to the product law with marginal distribution function D. Removing the clamping does not affect this convergence, by the displayed bound and the vanishing proportion of n<N.
Let U,V be independent with distribution function D. Continuity gives \Prob(U=V)=0, and exchangeability of this limiting pair gives
The boundary of the set \{(u,v):u<v\} is the diagonal, which has zero product mass. Weak convergence therefore yields
Since both logarithmic sizes have the same positive denominator, U_n<V_n is exactly \Pplus(n)<\Pplus(n+1). Applying the same continuity-set argument to v<u gives the reverse ordering limit as well. The symmetry used here belongs to the independent limiting law; no symmetry of the finite consecutive-integer pairs is assumed.
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