1 Introduction
Laughlin’s wave function describes a strongly correlated state at fractional filling of the lowest Landau level [7]. Haldane’s spherical geometry and pseudopotentials give a particularly simple parent Hamiltonian: each electron pair is penalized by the orthogonal projection onto relative angular momentum one [5]. The cubic Laughlin polynomial is its unique zero state at filling 1/3 with the spherical shift. A spectral gap separates this state from excitations. Stability asks whether that separation survives a weak external potential whose total many-particle norm grows with the area of the system.
We prove uniform stability for the full spherical interaction under bounded scalar potentials projected to the lowest Landau level. The potential may vary with system size and need not have any symmetry. The proof uses the uniform unperturbed Fock-space gap of [16], and derives the additional local estimates needed to pass from a gap at zero disorder to a gap on a fixed disorder interval.
1.1 Model and main result
For N\ge2, set q=3(N-1) and let S_q be the round sphere of radius \sqrt{q/2}. Magnetic length is one, so the sphere carries q flux quanta and has area 2\pi q. Let U_q be its one-particle lowest Landau level, equivalently the spin-q/2 representation of SU(2). On the entire antisymmetric space \bigwedge^N U_q, put
where P_{ij}^{(1)} projects the indicated pair onto total spin q-1. Each unordered pair has coefficient one. The normalized Laughlin vector spans the line generated by
If \Pi_q denotes the lowest-level projection and \varphi is a bounded real scalar function on S_q, its Toeplitz operator and many-particle perturbation are
Let E_0(N,\lambda,\varphi)\le E_1(N,\lambda,\varphi) be the two lowest eigenvalues, counted with multiplicity, of
Theorem 1.1 (Uniform scalar-disorder stability). There are constants \lambda_*>0, \Delta_*>0, and N_*<\infty such that, for every N\ge N_*, every real bounded measurable \varphi on S_{3(N-1)} with \|\varphi\|_\infty\le1, and every real |\lambda|\le\lambda_*,
In particular the perturbed ground state is unique.
The constants are uniform over the potential as well as particle number. Thus the theorem applies, in particular, to smooth potentials satisfying \max_{0\le k\le2}\|\nabla^k\varphi\|_\infty\le1 in the physical round metric. Its stronger amplitude-only formulation comes from the coherent-orbital representation of Toeplitz multiplication. The ground vector is allowed to move, and its energy is subtracted in the stability argument. Adding a constant to the potential changes only that energy. We give existential constants; the proof does not optimize the disorder threshold.
1.2 Historical context and the additional difficulty
Exact parent Hamiltonians have been central to the mathematical study of fractional quantum Hall states since the work of Trugman and Kivelson [20]. Haldane pseudopotentials also arise from suitable short-range limits of repulsive interactions, as proved by Seiringer and Yngvason [19]. The spectral gap is a separate quantitative question: identifying a zero polynomial does not control the energy of vectors perpendicular to it. Rougerie’s survey [17] discusses the gap problem and its role in the response of the Laughlin phase to perturbations.
Rigorous uniform gaps were established for truncated pseudopotentials in thin-cylinder and thin-torus geometries by Nachtergaele, Warzel, and Young [15] and Warzel and Young [21]. The unperturbed input used here concerns the full interaction on expanding round spheres [16]. We state its exact normalization in Theorem 2.2. In addition, we use and reproduce a strengthening of its four-body comparison: certain positive blocks that were discarded in obtaining the gap can be retained. This stronger estimate supplies the energy-loss construction below.
Another line of work controls density within the Laughlin-correlated class. Rougerie and Yngvason [18], followed by Lieb, Rougerie, and Yngvason [9], established incompressibility estimates for Laughlin functions multiplied by analytic symmetric factors. The sharp local density bound in [9] is averaged over mesoscopic disks. Our zero-mode estimate controls general local observables, with total cost proportional to the number of missing electrons; it is then combined with an estimate for states outside the zero space. Algebraic descriptions and recursions for pseudopotential zero modes were developed in [4, 11]. We use the symmetric-polynomial description and add quantitative bounds for its orthogonal branching.
General gap-stability theorems explain the role of local information. Bravyi, Hastings, and Michalakis [3] treated stability under sufficiently weak, suitably decaying local perturbations of commuting-projector models with topological-order conditions. Michalakis and Zwolak [12] proved stability for frustration-free lattice Hamiltonians under local topological-order and local-gap hypotheses. Subsequent infinite-volume formulations also retain local conditions in addition to a bulk gap [14]. Those hypotheses contain more information than a uniform global gap. For the spherical lowest Landau level, the local control needed here is established through flux pinning and a particle-loss evolution. The resulting relative-bound argument has the same purpose as local block diagonalization in the lattice theory, with a different source of control for the diagonal terms.
Our final continuation of the ground line uses the quasiadiabatic construction of Hastings and Wen [6] and the exact spectral-flow framework of Bachmann, Michalakis, Nachtergaele, and Sims [2]. It is applied inside a gap bootstrap, where its gap hypothesis is available. Locality is obtained using redundant localized frames. This connects to the continuum fermionic frame method of Bachmann and De Nittis [1]; we prove the finite-sphere estimates, including comparisons at neighboring fluxes, that the present argument requires. The propagation estimates follow the Lieb–Robinson method [8] and its fermionic form [13].
1.3 The proof and its reusable estimates
The main difficulty is extensive perturbation size: \|V_{N,q}(\varphi)\| can be of order N. A norm bound on the whole perturbation therefore gives a disorder interval that shrinks with particle number. We instead compare suitably centered local terms with the interaction energy. Two estimates make that comparison possible.
Local observables in zero spaces. At fixed flux q=3(N-1), write Z_{n,q}=\ker H_{n,q}. For an interaction W that is a bounded-density sum of uniformly localized neutral terms, we prove
where \Omega is the normalized filled Laughlin vector. This is Theorem 6.6; the constant is uniform in flux. Neutral means that a term preserves particle number; localization is defined precisely in Section 3. The linear dependence on N-n is essential.
To prove (1.4), we read a zero mode from one pole. Either the last orbital is empty, which removes one unit of flux and records a flag, or contraction in that orbital removes an electron and three units of flux. The branches are orthogonal and give coordinates for the entire zero space. The number of flags is the quasihole degree h=q+3-3n. At the filled flux it equals 3(N-n), three times the electron deficit; a one-hole sector below means h=1, not one missing electron. Pinning zeros at the pole realizes the required change of flux. The uniform Fock gap persists along that pinning deformation and gives local unitary transport. A history of branch choices then bounds a local observable by weighted flag values along the history. A first, slowly decaying weight supplies enough information to close a second estimate with an integrable weight. Rotation averaging yields (1.4).
Local descent of interaction energy. Extend the pair Hamiltonian to all particle sectors by H_q=\bigoplus_{n=0}^{q+1}H_{n,q}, with H_{0,q}=H_{1,q}=0, and let \mathcal N act as multiplication by n on the n-particle sector. On this Fock space we construct local particle-loss operators J_y such that (Theorem 7.1)
Each jump removes between two and a fixed number of particles. The associated completely positive evolution decreases interaction energy exponentially, and its expected particle loss is bounded by the initial energy. The construction first removes a pair and then partially empties a fixed neighborhood. A rotation average shows that the remaining pair correlations are paid for by the retained four-body blocks. This also proves a uniform energy cost for particle excess above Laughlin filling.
From descent to perturbation theory. For a small fixed \mu>0, the operator G=H_q+\mu(N-\mathcal N) controls both interaction energy and particle-number deficit or excess. If each neutral local term A_x annihilates \Omega, following its expectation through the loss evolution gives
The proof closes a quadratic inequality for the best relative-bound constant, using (1.4) at the limiting zero state (Proposition 8.1). This implication from local energy descent and linear electron-deficit control is useful independently of the particular flux construction. Finally spectral transport makes the derivative of the pulled-back perturbed Hamiltonian termwise centered in this sense. On the N-particle sector G=H_q, so integration gives a uniform lower bound above the transported ground state.
Section 2 fixes the algebra and zero-mode conventions. Sections 3–6 establish the local zero-mode estimate. Section 7 constructs the loss evolution, and Section 8 proves the relative bound and completes Theorem 1.1. Appendix A contains the retained-block comparison and its finite arithmetic data.
2 Lowest Landau level and zero modes
We fix the normalization of the interaction before discussing locality. The exterior-algebra formulation is useful because both the pinned Hamiltonians and the particle-loss evolution change particle number. Throughout the paper, constants are independent of flux and particle number unless an explicit dependence is indicated. A statement for large flux means that its threshold is independent of the particle sector.
2.1 Coherent orbitals and pair annihilators
Let q\ge1 be an integer. The sphere S_q has radius \sqrt{q/2}, area 2\pi q, and magnetic field one. The lowest Landau level U_q is the spin-q/2 representation of SU(2). We use homogeneous polynomials of degree q in spinor coordinates (z_0,z_1), with invariant inner product normalized so that
is an orthonormal basis. This normalization identifies U_q unitarily with the physical lowest Landau level; it does not rescale any operator. Relative to a chosen north pole, j=0 is the north orbital and j=q the south orbital.
Write k_x for the unit coherent vector at x\in S_q, defined up to a phase by the Riesz vector for evaluation at x. Its components in the axis basis have squared moduli
Schur’s Lemma and the trace give the resolution
In particular the density \kappa_q is uniformly bounded. For a bounded measurable real function \varphi, the Toeplitz operator is
Indeed the quadratic form on the right is the integral of \varphi times the product of the two evaluated lowest-level sections, which is the quadratic form of compression of multiplication by \varphi.
The fermionic Fock space and number operator are
Increasing wedges of orthonormal vectors have norm one. For a\in\bigwedge^k U_q, let B(a) be the adjoint of left wedge multiplication by a. Thus B is conjugate-linear, B(a\wedge b)=B(b)B(a), and c_j=B(e_j) satisfy the canonical anticommutation relations. For a one-particle vector f we also write c(f)=B(f). For an operator on \bigwedge^k U_q, its lift to Fock space is the linear extension of
The lift preserves positivity and rotations. It vanishes on sectors with fewer than k particles and equals its argument on the k-particle sector.
Let V_q\subset\bigwedge^2 U_q be the spin-(q-1) summand. Its orthonormal axis basis v_p, 0\le p\le2q-2, can be written as
where 1\le b\le2q-1. The formula follows by lowering the highest vector e_0\wedge e_1. For its normalization, the sum over ordered i,j with i+j=b is a hypergeometric second moment: its total mass is \binom{2q}{b} and the mean of (j-i)^2 is b(2q-b)/(2q-1). Dividing by two gives Z_{q,b}. We set B_p=B(v_p). The interaction is
On n particles this is exactly \sum_{i<j}P_{ij}^{(1)}, with coefficient one for each unordered pair. One way to check the coefficient is to identify a unit wedge with its normalized antisymmetric tensor: contraction in two prescribed tensor positions is B(a)/\sqrt{\binom n2}, and summing the \binom n2 pair projections gives (2.6).
We shall also use the wedge maps
In particular V_q\otimes V_q uses ordered pairs. This convention fixes the coefficient of the four-body term in the normal-ordered square used in Appendix A.
2.2 The zero spaces and the unperturbed input
The polynomial and second-quantized descriptions of these kernels are closely related; see [4, 11] for algebraic constructions of pseudopotential zero modes. Put Z_{n,q}=\ker H_{n,q} and let P_{n,q} be its orthogonal projection. When all sectors are being considered, write Z_q=\ker H_q and P_q for the Fock-space zero projection.
Lemma 2.1 (Polynomial description). For n\ge1, a vector lies in Z_{n,q} if and only if its polynomial has the form
where S is symmetric and homogeneous of degree h=q+3-3n in each spinor. Consequently Z_{n,q}=\{0\} when h<0, and, when h\ge0,
At q=3(N-1) the space Z_{N,q} is the Laughlin line, and every nonempty zero sector has particle number at most N. The vacuum sector Z_{0,q} has dimension one.
Proof. Positivity of the pair terms says that a zero vector has no pair relative-angular-momentum-one component. An antisymmetric polynomial of the same homogeneous degree in each of two spinors vanishes when the spinors coincide. Separate homogeneity extends that vanishing to proportional spinors, so the irreducible bracket [z_1,z_2] divides it. Dividing by the bracket and then setting z_1=z_2=z gives an equivariant map to the degree-(2q-2) polynomials in z, the spin-(q-1) representation. This map is nonzero on e_0\wedge e_1 and hence is onto. Its kernel is exactly divisibility by the bracket cubed: the divided polynomial is symmetric and separately homogeneous, and if it vanishes on the diagonal it is divisible by the bracket; the resulting quotient is antisymmetric and therefore divisible by the bracket once more. By the two-spin decomposition, the map detects precisely the spin-(q-1) summand. Thus absence of that component is equivalent to cubic divisibility.
It follows that every pair bracket cubed divides the polynomial. The distinct pair brackets are nonassociate irreducible polynomials; unique factorization makes their product divide it. Dividing by the cubic product changes antisymmetry to symmetry and leaves degree q-3(n-1) in each variable. This proves both directions of (2.8). A symmetric polynomial with individual degree h has the symmetrized monomial basis indexed by 0\le j_1\le\cdots\le j_n\le h, giving the binomial dimension. The remaining claims follow at once, with the vacuum treated separately.
The quantitative unperturbed result used in this paper is the following Fock-space gap theorem. We recall it with the normalization just fixed; its proof is in the companion manuscript [16, Theorem 1.1 and Corollary 1.2].
Theorem 2.2 (Uniform unperturbed gap). Let \gamma_*=4616733319001/10^{14}. For every 0<\gamma<\gamma_* there is q_\gamma such that
on all of \mathcal F_q. In particular, for all sufficiently large N and q=3(N-1),
The all-sector statement gives separation of the spectrum from zero. We use it for zero-space transport, including particle numbers below Laughlin filling. The extra four-body comparison needed for energy descent is proved separately in Appendix A; it is stronger than (2.9).
2.3 Geometric scales
An axis on S_q gives latitude coordinate m=q\sin^2(\theta/2) and longitude \phi. In these coordinates dA=dm\,d\phi. We use
Here v is an end-distance weight; the potential is always denoted by \varphi. The width w converts index distance to physical distance, including in the polar caps. Section 3 proves the geometric estimates that make these scales useful for local operators.
3 A local calculus in the lowest Landau level
The orbital basis diagonalizes rotations about an axis, but its middle orbitals extend around an entire latitude. We first replace that basis by a redundant family localized in both latitude and longitude. Its analysis map embeds the physical fermions into a larger collection of fermionic modes with a genuine notion of spatial support. The use of localized frames to obtain continuum fermionic locality is developed in [1]; we give the finite-sphere construction and estimates needed here. We then prove the propagation and functional-calculus estimates needed to manipulate local operators. All constants in this section are independent of the flux and the particle number.
3.1 Localized frames and auxiliary fermions
Fix an axis and write
The area form is dm\,d\phi. Away from the two polar balls of fixed radius, changing m by w_q(m) or changing \phi by 1/w_q(m) moves a bounded physical distance. The following elementary comparisons will also be used at the poles, with u,v\geq1:
Indeed m is one half the squared chordal distance from the north pole; the triangle inequality gives the assertion for u, and the south pole gives it for v. The assertion for w_q follows from their product.
Here is an explicit frame construction. Choose a nonnegative smooth function \eta, supported in (-2,2) and positive on [-1,1], and a smooth function 0\leq\chi\leq1 on [0,1] equal to one on [0,1/2] and zero on [2/3,1]. For positive integers k use the nonzero functions
Divide each by the square root of the sum of their squares. The resulting windows \xi_a satisfy
where I_a is an interval of integers, m_a is the corresponding window center, and w_a=w_q(m_a). At the first few windows the constants absorb the bounded widths. Every index belongs to a bounded number of intervals. To check the difference bound, extend each expression smoothly in j. On a northern window k\asymp\sqrt{1+j}\asymp w_q(j); each derivative of \sqrt{1+j} costs at least w_q(j)^{-1}, and derivatives of \chi(j/q) cost q^{-1}\leq Cw_q(j)^{-1}. The denominator is bounded above and below, and obeys the same estimates. The southern windows have the identical verification.
For a window bearing the index k, choose the fixed integer L_a=16(k+1), which is larger than the diameter of the full bump support before restriction to [0,q]. Thus L_a\asymp w_a and, for a northern window, its Fourier length is independent of q. For 0\leq\ell<L_a set
where e_j is the normalized orbital of Section 2. Repeated points near the poles are retained as distinct slots. Their multiplicities are bounded. Write \Lambda_q for this set of slots. Fourier orthogonality and (3.3) give the exact identity
Thus \mathsf S_q\psi=(\langle z_x,\psi\rangle)_{x\in\Lambda_q} is an isometry from U_q to \ell^2(\Lambda_q). The slots have bounded density:
The window centers have bounded density in radial physical distance, and their circles carry O(w_a) slots with spacing bounded below except inside the bounded polar balls. This proves (3.6). Figure 1 shows the two scales in this construction.
Figure 1: The index window has width comparable to w_a; its Fourier phases place a comparable number of slots around the latitude. Together with unit-order radial spacing, this gives bounded slot density in physical distance. The drawing is schematic: dashed circles indicate rapidly decaying tails, not compact spatial support.
We need two quantitative consequences of this construction. Let k_y be a normalized coherent orbital centered at y.
Lemma 3.1 (Uniform frame localization). For every D there is C_D such that
For two frames constructed as above, possibly with different axes, their atoms satisfy the same bound with k_y replaced by an atom centered at y. For each fixed integer J, (3.7) also holds, with constants depending on J, for every rotated polar orbital e_j(y) with 0\leq j\leq J.
Proof. Choose the axial gauge and azimuth convention in which the coefficient of e_j in k_y is e^{ij\phi_y}p_{q,m}(j)^{1/2}. Its modulus is
They obey, after extension by zero outside [0,q],
Here and below finite differences may shift the argument by a fixed number of indices, which only changes the constant. We include a verification to specify uniformity near the ends. First put p=m/q and \sigma^2=qp(1-p), so w_q(m)^2=1+q\sigma^2/(q+1)\asymp1+\sigma^2. Fourier inversion of a binomial law of variance \sigma^2 gives
For 0<p<1, tilt the law by e^{\lambda j}. Its new parameter is p_\lambda=pe^\lambda/(1-p+pe^\lambda), and its variance differs from \sigma^2 by a factor between e^{-|\lambda|} and e^{|\lambda|}. Therefore the centered log moment generating function satisfies \log\mathbb E e^{\lambda(X-m)}\leq\sigma^2\lambda^2 for |\lambda|\leq1/2. At z=j-m, choose \lambda=z/(2(\sigma^2+|z|)). The exact tilting identity and the preceding point-mass bound give
The cases p=0,1 are direct. This proves every polynomial tail bound with the required height, uniformly also when w_q(m) is bounded.
For the derivative gain first assume w_q(m)^2\geq16(l+1), and let h=\min(m,q-m)\asymp w_q(m)^2. Interpolate the square root of the binomial probability by gamma functions, writing the resulting positive function as F(x). Put \psi=(\log\Gamma)' and \psi_1=(\log\Gamma)''. On |x-m|\leq h/2, the explicit formulas
and the positive-real polygamma series give |(\log F)'(m)|\leq Cw^{-2}, (\log F)''(x)\leq-cw^{-2}, and |(\log F)^{(k)}(x)|\leq C_kw^{-k} for k\geq2. Stirling’s inequalities give F(m)\leq Cw^{-1/2}. Differentiating F=e^{\log F} consequently proves
If |j-m|\leq h/4, integrate this derivative over the unit cube that represents \Delta^lF(j); the entire stencil stays in the displayed interval. Outside that region, each nonzero stencil entry has |j+a-m|\geq cw^2, 0\leq a\leq l. Equation (3.9) then supplies an exponential in that distance, which pays both w^{-l} and every polynomial tail. This also handles stencils crossing an endpoint. Finally, if w^2<16(l+1), bound the finite difference by its l+1 values and use (3.9); the factor w^{-l} is now a constant depending only on l. This completes the proof of (3.8), including the bounded-width regime.
Insert (3.8) in (3.4). For windows whose radial centers are a bounded distance apart, their widths are comparable; summation by parts l times gives the factor (1+w_a|\phi_x-\phi_y|)^{-l}, with angular difference modulo 2\pi. The absolute sum before summation by parts is bounded. For separated radial windows, the tail in (3.8) first supplies arbitrary powers of radial distance. The ratios of the widths cost only polynomial powers by (3.2). Spending additional tail orders therefore gives the same angular estimate. Radial distance plus the shorter latitude arc bounds the spherical distance from above, proving (3.7).
The coherent resolution of the identity has density (q+1)/(2\pi q) with respect to area. Inserting it between two frame atoms reduces the frame-to-frame bound to
The inequality follows by dividing the integral into the sets where d(x,z)\geq d(x,y)/2 and where d(z,y)\geq d(x,y)/2. Finally
where \vartheta is the angle between y and z. For bounded j, this is bounded by C_j(1+d(y,z))^{2j}e^{-c d(y,z)^2}; increasing the constant covers bounded q. Inserting the coherent resolution once more proves the last assertion.
Lemma 3.2 (Common frames for nearby fluxes). For each fixed d_0, frames at fluxes q and t with 0\leq q-t\leq d_0 may be embedded in the same slots so that index identification i_{q,t}:e_j^{(t)}\mapsto e_j^{(q)}, j\leq t, satisfies the exact identity \mathsf S_t=\mathsf S_q i_{q,t}. All preceding estimates remain uniform. In the northern third the windows can be chosen from one system independent of the flux; there one may use the common metric with radial variable \sqrt{1+m}.
Proof. Use the windows and Fourier lengths at flux q for both spaces, and restrict their index sequences to 0\leq j\leq t for the smaller space. Equation (3.5) still holds on those indices. Only a bounded number of end indices have been removed. The windows meeting them have bounded width, or have rapidly small tails in the estimates in which an endpoint extension occurs. The slot positions for the two sphere metrics differ by a bounded distance; the constants may depend on d_0. For all sufficiently large q, every window centered in the northern third has its full support below q/2, because its width is O(\sqrt q). On these supports the construction uses only \eta(\sqrt{1+j}-k) and their fixed normalization, and their Fourier length is the fixed integer 16(k+1). These complete slot vectors are therefore independent of q in index coordinates. The buffer between q/3 and q/2 permits changing the frame outside this region without changing its northern slots. Bounded fluxes may use pairwise padded frames; no long sequence of common slots is needed there.
Whenever operators at these two fluxes are subtracted, we first use i_{q,t} and extend the smaller operator by the identity on the added orbital modes. Thus, under the graded decomposition \mathcal F_q=\mathcal F_t\,\widehat\otimes\, \bigwedge\operatorname{span}\{e_{t+1},\ldots,e_q\}, the padded operator is A\widehat\otimes I. Extra modes are put in their vacuum only when comparing states or taking the physical compression.
The fermionic Fock space over \ell^2(\Lambda_q) is a graded tensor product of two-dimensional slot spaces. The exterior isometry \Gamma(\mathsf S_q) identifies \mathcal F_q with the subspace in which the orthogonal complement of \mathsf S_qU_q is vacant. A physical operator is an operator in the CAR algebra generated by \mathsf S_qU_q, extended as the identity on the complementary modes. It preserves that vacant-complement subspace. For X\subset\Lambda_q, let \mathfrak A(X) be the CAR algebra of its slots. Put \mathcal N_{\mathrm{slot}}=\sum_{x\in\Lambda_q}c_x^*c_x. An operator has number grade k\in\mathbb Z if [\mathcal N_{\mathrm{slot}},A]=kA, and parity \epsilon_A\in\{0,1\} if (-1)^{\mathcal N_{\mathrm{slot}}}A(-1)^{\mathcal N_{\mathrm{slot}}} =(-1)^{\epsilon_A}A. Operators of even parity on disjoint sets commute; homogeneous operators obey the graded relation
All Hamiltonians below have even parity. Local expansions can be projected onto any prescribed number grade by averaging the gauge action of the total slot number \mathcal N_{\mathrm{slot}}. This action preserves every slot algebra and does not increase approximation errors. On physical operators its grading agrees with that of the physical number operator \mathcal N.
3.2 Local norms and summation
For a center x, an operator A, and l>0, define
We call A rapidly local at x if this is finite for every l, with bounds uniform in the volume under consideration. An interaction is a family A_x integrated against a measure whose mass in every unit ball is bounded. A bound of size a(x) means \|A_x\|_{x,l}\leq C_l a(x) for every l. A positive function a is called tempered if, for fixed C,\kappa,
The constants in estimates involving a may depend on C,\kappa. Powers and products of u,v,w are examples.
Taking near-best approximations at radii 2^k and subtracting successive ones gives a ball decomposition
Conversely such a decomposition implies the approximation bound, with any slightly smaller exponent. We use this elementary equivalence to pass between operators and interactions on balls.
An observable supported initially on a large ball needs a separate convention. A family has core radius r and amplitude a if
where the geometric constant C_* is independent of D. The amplitude may contain a specified power of r. This convention does not assert that every centered norm (3.10) is bounded by Ca without a further radius factor.
Lemma 3.3 (Shells outside a fixed core). If (3.13) holds with r\geq1, there is a decomposition A=\sum_{\nu\geq0}A_\nu with A_\nu\in\mathfrak A(B_{C_*2^{\nu+1}r}(x)) and \|A_\nu\|\leq C_Da2^{-\nu D} for every D. Consequently, for each fixed B\geq0,
Proof. Take approximants at radii C_*2^\nu r and telescope, starting with the first approximant as the core. The core norm is Ca; the other differences are bounded by the two adjoining errors in (3.13). Sum with any D>B+1 to obtain (3.14).
Lemma 3.4 (Products, commutators, and weighted sums). The following bounds are uniform over the slot systems above.
- (i)
Products of operators rapidly local at the same center, and adjoints, preserve rapid locality. If A,B are centered at x,y, respectively, with bounded local norms, then \|[A,B]_{\mathrm{gr}}\|\leq C_D(1+d(x,y))^{-D} for every D.
- (ii)
If A is rapidly local at x and a rapidly local interaction K_y has tempered size a(y), then [\int K_y\,dy,A]_{\mathrm{gr}} is rapidly local at x, of size a(x) times the local bounds of A.
- (iii)
Suppose A is even, \|A\|_{x,l}\leq1, and J_y has bounded rapid local norms. With D=1+d(x,y) and C_{xy}=[A,J_y],
\|C_{xy}\|\leq C D^{-l},\qquad \|C_{xy}\|_{x,l}\leq C,\qquad \|C_{xy}^*C_{xy}\|_{x,l}\leq C D^{-l}. \tag{3.15}
For an operator initially supported in B_r(x), the corresponding core estimates cost a fixed polynomial in r. At distances larger than a fixed multiple of r, any prescribed decay order is available.
Proof. The product estimate follows from
For the commutator use approximations of radius less than d(x,y)/3; their graded commutator vanishes. For the weighted assertion expand both factors as in (3.12). Terms with disjoint balls vanish, while intersecting balls of radii R,S require d(x,y)\leq R+S. The number or measure of their possible centers is O((1+R+S)^2), and (3.11) costs at most C(1+R+S)^\kappa. To obtain an output moment of order D, bound these costs by C(1+R+S)^{D+\kappa+2} and choose input decay order larger than D+\kappa+6. The two geometric sums then converge. This argument also permits assigning each output term to the center of either input; that convention will be used for differences of interactions.
For (3.15), the first estimate follows by the disjoint-ball argument at exponent l. For approximation radii r\leq3D, use zero as an approximant to C_{xy}, giving r^l\|C_{xy}\|\leq C. For r>3D, approximate A in B_{r/3}(x) and J_y in B_{r/3}(y); their commutator is supported in B_r(x) and has error Cr^{-l}. Thus the second estimate holds. Apply the product estimate with the small norm \|C_{xy}\|\leq CD^{-l} on one factor to obtain the third estimate. Finally a ball B_r(x) contains O((1+r)^2) slots, and tempered ratios within it cost O((1+r)^\kappa). The same sums give the stated polynomial core costs. For tails beyond Cr, the distance from the original ball is comparable to the tail radius, so increasing a tail order does not increase the core-volume exponent.
Corollary 3.5 (The physical interactions). The unperturbed Hamiltonian H_q and the Fock lift of any bounded real scalar symbol \varphi have physical, neutral, Hermitian rapid interactions of uniform sizes C_D and C_D\|\varphi\|_\infty, respectively.
Proof. Coefficient localization gives operator-norm localization directly. If E_R is the one-particle projection onto slots in B_R(x), the CAR identity \|c(f)\|=\|f\|_2 gives
For f=k_x or a bounded polar mode at x, Lemma 3.1 and the slot count (3.6) make the right side at most C_D(1+R)^{-D} for every D; the approximating annihilator is supported in B_R(x).
The coherent resolution gives
For H_q, the highest pair vector is v_0=e_0\wedge e_1. Schur’s Lemma on the spin-(q-1) pair space and its dimension 2q-1 give, with Haar mass one,
The product B(gv_0)=c(ge_1)c(ge_0) is rapidly local at the rotated pole by Lemmas 3.1 and 3.4. Its phase along the stabilizer disappears in its square, so the center measure on the sphere has density (2q-1)/(2\pi q). This and (q+1)/(2\pi q) are uniformly bounded. The same two lemmas localize c^*(k_x)c(k_x). No derivative of \varphi enters either the representation or its bound.
3.3 Propagation and spectral filters
We next establish that a time filter preserves this local calculus. The relevant propagation bound is needed only with arbitrary polynomial decay, which permits a direct truncation argument. The underlying commutator iteration is the Lieb–Robinson method [8], in its graded fermionic form [13]; its use with time filters is the locality mechanism behind quasi-adiabatic continuation and spectral flow [6, 2].
Lemma 3.6 (Propagation of local observables). Let K be self-adjoint and even, with a rapidly local interaction of uniform size. Write \tau_t^K(A)=e^{itK}Ae^{-itK}. For each D there are D' and M_D, independent of volume, such that
The assertion holds also for time-dependent generators with the same uniform bounds. In particular evolution over a bounded parameter interval preserves rapid locality. If A is supported in B_r(x), the error in approximating \tau_t^K(A) on B_R(x), for R\geq C(r+(1+|t|)^4), is bounded by C_D\|A\|(1+r)^2R^{-D}.
Proof. Use (3.12) to write K as a sum of terms on balls. Taking Hermitian and even parts makes each term Hermitian and even without changing the total or its estimates. First retain only terms of diameter at most \ell. For this truncated interaction define
Uniform summability, including the number of sites in X, gives \sup_a\sum_b M_{ab}e^{d(a,b)/\ell}\leq C; indeed each retained distance is at most \ell, and the ball-volume costs are polynomial. The iterated commutator inequality, with internal evolution removed unitarily at each step, therefore gives
for A\in\mathfrak A(X) and B\in\mathfrak A(Y). For completeness, the nth iterated integral contributes |t|^n/n! times a chain of n matrix factors M. Multiplication by e^{d(X,Y)/\ell} is bounded by the product of the exponential weights along the chain. Summing the intermediate sites gives C^n, and summing n gives (3.18). Evenness of the generator makes the same calculation valid for odd A,B with the graded commutator.
Restore the removed terms using Duhamel’s formula. For each removed ball term use the smaller of the trivial commutator bound and (3.18). The centers within distance C\ell(1+|t|) of X, together with the radius of that term, occupy at most a polynomial volume. Outside that region the exponential bound is summable. Consequently, for every s, the restoration error is at most
when X\subset B_r(x). To see the power allowance explicitly, a removed term of radius a contributes its norm times at most C(1+r+\ell(1+|t|)+a)^2 possible centers and at most C(1+a)^2 sites. Its arbitrarily high radius moment makes the sum over a>\ell/2 bounded by the right side of (3.19), after increasing the input moment by s+6.
Now let R\geq C(r+(1+|t|)^4) and choose \ell=R^{1/3}. The truncated evolution differs from the evolution generated by its terms contained in B_R(x) by C\|A\||X|\operatorname{poly}(R)e^{C|t|-cR^{2/3}}. This is again Duhamel’s formula and (3.18), summed over the boundary terms. Both restoration errors are bounded by C_D\|A\||X|R^{-D}, choosing s sufficiently large in (3.19). This supplies an approximation in \mathfrak A(B_R(x)). At smaller radii use the norm bound \|\tau_t(A)\|=\|A\|. Since |X|\leq C(1+r)^2, this proves the assertion for supported A and then, by (3.12), (3.17). The proof uses only uniform bounds on the interaction at each time, so also proves the time-dependent assertion.
Lemma 3.7 (Time filters). Suppose F\in L^1(\mathbb R) and \int(1+|t|)^j|F(t)|\,dt<\infty for every j. Under the hypotheses of Lemma 3.6,
is rapidly local whenever A is, with uniform bounds. The same is true for a finite measure consisting of such a function and a mass at zero. Number grade and physicality are preserved when K is neutral and physical. Suitable symmetry of F preserves adjoints.
Proof. Integrate (3.17). The approximation norm is a seminorm up to its operator-norm summand, so the integral of local approximants gives the required estimate. The remaining assertions follow directly by commuting the evolution with gauge transformations, the physical algebra, and adjoints.
The frequency functions used below are smooth, vanish on an interval about zero, and have tails proportional to 1/\omega on one or both half-lines. Their inverse Fourier transforms satisfy the hypotheses of Lemma 3.7. Here is a convenient verification. Every positive-order derivative of such a multiplier is integrable, so integration by parts gives arbitrary powers of decay for |t|\geq1. For 0<|t|<1, split the frequency integral at |\omega|=|t|^{-1}. The inner portion is O(1+|\log|t||), and one integration by parts on the outer portion is O(1). Thus the possible singularity at zero is integrable. A smooth compactly supported multiplier has a Schwartz kernel. These facts cover both spectral transport and the filters that retain only small energy differences.
Lemma 3.8 (Weighted differences). Let K,K' satisfy Lemma 3.6 uniformly, and assume K-K' has a rapidly local interaction of tempered size a(z). For a rapidly local A centered at x,
The same conclusion holds after an all-moments time filter, and for differences of bounded-parameter evolutions. If the input itself changes by local size b(x), its separate contribution is Cb(x). All estimates retain the product of a local input size and a(x). If A\in\mathfrak A(B_r(x)), put s=\kappa+2, with \kappa from (3.11). The difference has operator norm at most
For R\geq C_*(1+r), with a fixed geometric constant C_*, it has an approximation supported in B_{r+R}(x) with error at most
Thus the power of the initial radius is independent of the tail order. If the differing interaction vanishes throughout a ball of radius d about x, the bounds for a fixed rapidly local input gain arbitrary inverse powers of 1+d.
Proof. Use the exact formula
Apply Lemma 3.6 to the inside observable, Lemma 3.4(ii) to the commutator, and Lemma 3.6 once more to the outside evolution. The tempered inequality (3.11) is precisely what allows the insertion at z to be charged to a(x). All time costs are polynomial and therefore integrable against the specified filters. The time-dependent version follows from its identical Duhamel formula. Linearity handles a changed input.
We give the additional radius bookkeeping for (3.22)–(3.23). For a ball decomposition about x, use the weighted sum \sum_R(1+R)^p\|A_R\|. Lemma 3.6 bounds its evolved value by C_p(1+|t|)^{4p} times its initial value. Indeed, for a radius-r input, begin a dyadic decomposition at Q=C(1+r+(1+|t|)^4). The core contributes C\|A\|Q^p; the subsequent shells contribute at most C_M\|A\|(1+r)^2\sum_{R\geq Q}R^{p-M}. Choosing M>p+2 bounds this by C_p\|A\|Q^p. The weighted insertion estimate in the proof of Lemma 3.4 costs s=\kappa+2 powers of the input radius. Duhamel at p=0 proves (3.22).
For the tail first take |t|\leq cR^{1/4} in the Duhamel integrand, with c>0 a sufficiently small fixed constant; bounded R are covered by (3.22). Fix also a small \varepsilon>0. Choose \varepsilon,c and then C_* so that the propagation lemma applies both from radius r to r+\varepsilon R and from radius r+3\varepsilon R to r+R. This requires only fixed constants: if C is the constant in that lemma, take \varepsilon<(100C)^{-1}, c^4<\varepsilon/(10C), and C_*>100C/\varepsilon. Cut the inner evolved observable at radius r+\varepsilon R. Its remaining shells have weighted sum of order s at most C_M\|A\|(1+r)^2R^{s-M}, by the short-time bound in Lemma 3.6; their commutator with the insertion has the same bound times Ca(x). In the retained part, discard insertion terms of radius greater than \varepsilon R. Their arbitrary radius moments give an error C_Ma(x)\|A\|R^{-M}. The remaining commutator is supported in B_{r+3\varepsilon R}(x) and has norm at most Ca(x)\|A\|R^s. Evolving it in the outside factor of Duhamel and using the short-time propagation estimate gives an approximation on B_{r+R}(x) with error C_Ma(x)\|A\|R^{s+2-M}. Choose M in each of these three bounds larger than the requested order plus s+4, and integrate over an interval of length at most R^{1/4}. This gives the stated tail bound for short times. For |t|>cR^{1/4}, use (3.22) and (1+|t|)^{4D}(1+R)^{-D}\geq c_D.
Finally suppose an insertion ball of radius a can occur only if its center z satisfies d(x,z)+a\geq d. If that ball meets an input shell of radius R, then d\leq R+2a. Inserting (1+d)^{-M}(1+R+2a)^M into the shell summation proves the last assertion, after increasing the input moments. This includes changes supported outside a common comparison region.
To specify physical compression, let S:U_q\to K_S and T:U_q\to K_T be two slot analysis isometries. Write J_S=\Gamma(S) for the vacuum-complement embedding and \iota_T for the embedding of the physical CAR algebra into the output slots, acting as the identity on complementary modes. The map that we estimate is
When T=S this is compression followed by identity extension; it is a unital contractive completely positive map. On physical input operators it is simply change of frame.
Lemma 3.9 (Compression, changes of frame, and smooth functions). The map (3.24), for the frames of Lemma 3.1, preserves rapid locality. An operator supported in B_r(x) remains localized about that ball, with polynomial core costs and arbitrary inverse-power tails outside B_{Cr}(x). If A=A^* is bounded and rapidly local, and f is smooth on a neighborhood of its spectrum, then f(A) is rapidly local. The constants depend on finitely many local bounds and derivatives for each requested decay order.
Proof. Put two slot spaces side by side. If S,T are their analysis isometries, the partial isometry TS^* has rapidly decaying matrix entries by Lemma 3.1. On their direct sum, the anti-self-adjoint one-particle operator
rotates the two physical subspaces into each other through angle \pi/2 and acts as zero on their complements. Its second quantization is a bounded-strength, rapidly local quadratic interaction: absolute row sums and every distance moment are bounded by (3.6). Lemma 3.6 applies over this fixed angle. Conjugate A\otimes I by this rotation and take the vacuum expectation in the entire first slot copy, retaining the entire second copy. On a CAR monomial, the physical components have moved from S U_q to T U_q, while the complementary components in the first copy are evaluated in their vacuum. The resulting map is exactly (3.24), including for odd monomials; linearity gives the identity for every operator. Vacuum expectation is contractive and preserves support in the doubled slot geometry. This proves the assertion, and S=T gives re-embedded physical compression. In particular no projection onto the output complementary vacuum is left in the resulting operator.
For the functional-calculus assertion extend f smoothly to a compactly supported function on \mathbb R. If A_r approximates A locally, its Hermitian part does so with the same error. The Fourier formula and Duhamel’s identity give
Since f(A_r) belongs to the same local algebra, the approximation bounds follow. A constant value of f contributes only a scalar identity, which is local in every ball.
3.4 Pair rows and diagonal symbols
The coherent orbit representations already prove locality of the unperturbed Hamiltonian and bounded scalar perturbations. Pinning zeros will deform the pair coefficients and remove full rotation invariance. To control those deformations and compare neighboring fluxes, we now prove a local calculus directly for angular-momentum rows and diagonal orbital symbols.
Write Q_b=B_{b-1} for the normalized pair annihilator with index sum b in (2.5), 1\leq b\leq2q-1. Define its ordered coefficients by
In this formula the sum for S_b is over ordered i. With a fixed choice of annihilator sign, Q_b=2^{-1/2}\sum_{i+j=b}a_b(i)c_jc_i =\sqrt2\sum_{i<j,\,i+j=b}a_b(i)c_jc_i. Changing this common sign leaves every square unchanged.
Lemma 3.10 (Pair profiles and local row squares). With m=b/2 and w=w_q(m), the zero-extended coefficients satisfy
There are pair annihilators L_{\nu,\phi}, rapidly local with uniform bounds about centers x_{\nu,\phi}, and a measure d\mu of bounded mass per unit ball, such that
The construction is linear in the row coefficients. In particular symbol bounds (3.26) with an additional tempered factor give local bounds with that factor; the same holds for differences of row families in common frames.
Proof. Vandermonde’s identity identifies \binom qi\binom q{b-i}/\binom{2q}{b} as a hypergeometric law of mean b/2 and variance b(2q-b)/(4(2q-1)). Multiplying its second centered moment by four proves (3.25). The moment formula itself also follows directly by applying i\binom qi=q\binom{q-1}{i-1} twice and Vandermonde’s identity.
Here are symbol estimates that include the dependence on the moving row center. Set
and
where the gamma formula defines the smooth extension. Then a_b(i)=-2t e^{E(m,t)}/\sqrt{T(m)}. The gamma duplication formula gives the exact expression
For m,q-m\geq1/2, Stirling’s inequalities yield T(m)\asymp w_q(m)^3. Its logarithmic derivatives of order r\geq1 are bounded by C_r(u^{-r}+v^{-r}). These derivative assertions can be obtained directly by differentiating Euler’s gamma product: for k\geq1,
In the region |t|\leq c\min(u,v), the second derivative \ell_q'' is negative and comparable in magnitude to u^{-1}+v^{-1}\asymp w^{-2}. Thus E(m,t)\leq-ct^2/w^2. Differentiating E in i and b gives polynomials in t/w, with one factor w^{-1} per derivative; (3.28) has the same property. The discrete product rule, or integration of these derivative bounds over unit cubes, proves (3.26) in this region. There is also a global Gaussian bound, including the ends: convexity of the trigamma function \psi_1=(\log\Gamma)'' and \psi_1(x)\geq1/x give
Since E(m,0)=E_t(m,0)=0, we have E(m,t)\leq-ct^2/w^2 on the entire allowed interval. Outside the central region |t|/w\geq cw when w is large, so increasing the tail order pays all derivative and endpoint-extension factors. The rows with bounded w require only bounded finite differences. This proves the full uniform estimate without differentiating a lattice normalization sum.
Choose smooth windows \zeta_\nu(b) with \sum_\nu\zeta_\nu(b)^2=1, supported on intervals of length O(W_\nu) around b=2M_\nu, where W_\nu=w_q(M_\nu). The construction (3.3), with m=b/2, supplies them. Define
Fourier orthogonality proves (3.27) exactly. The radial centers have bounded density in physical distance, while their circle lengths are comparable to W_\nu outside the polar balls. Hence \mu has bounded mass on unit balls.
After removing its linear phase e^{-i(i+j)\phi}, the two-index coefficient of L_{\nu,\phi} has height O(W_\nu^{-1}), and every mixed finite difference of orders r,s costs W_\nu^{-r-s}. Its tails are arbitrary powers of 1+|i-M_\nu|/W_\nu+|j-M_\nu|/W_\nu. To express it in slot fermions, multiply in each index by the window coefficients from (3.4) and sum. On comparable windows, repeated summation by parts in both indices gives, for arbitrary D, coefficients bounded by
for the slot monomial c_xc_y. The height is bounded because the two summation lengths are O(W_\nu), the coefficient height is O(W_\nu^{-1}), and the two Fourier normalizations contribute O(W_\nu^{-1}). Noncomparable windows have radial separation; their scale ratios cost polynomial powers by (3.2), paid by increasing the radial tail orders. This proves the displayed bound for all slots. Its absolute sum, including every distance moment, is bounded by (3.6). Since \|c_xc_y\|\leq1, truncating that sum proves rapid locality in operator norm. Products give locality of L_{\nu,\phi}^*L_{\nu,\phi}. Each operation used was linear in the row coefficients before the final square; keeping any extra tempered factor proves the last assertion.
For a smooth real function a on [0,q], fix a constant C_0 larger than the window-support constants and define
The order-zero term is part of this seminorm. Scaled derivatives, rather than merely bounded unscaled derivatives, are necessary: orbital oscillations on the scale of one index translate an operator around a macroscopic latitude.
Lemma 3.11 (Diagonal symbols). Suppose A(m)>0 is tempered with exponent \kappa and \mathfrak s_K(a;m)\leq C_KA(m) for every integer K\geq0. Then D_q(a)=\sum_j a(j)c_j^*c_j has a physical, neutral, Hermitian interaction of size A(m). For each output approximation order D, only the seminorms through K_D=\lceil4D+4\kappa+40\rceil are needed. The construction and the estimate are linear in the symbol, so the same assertion holds for differences of symbols.
Proof. Insert the analysis map on both sides of the diagonal one-particle matrix. The slot matrix elements are
The two radial windows must overlap, so their widths are comparable and their radial physical separation is bounded. Taking K finite differences of the summand and summing by parts gives the bound C_K A(m_1)(1+d(x_1,x_2))^{-K}. The normalization cancels the length of the summation interval. At bounded-width end windows the same statement follows from finite sums; all involved slots are inside a bounded polar ball.
Assign the quadratic monomial to x_1, and pair it with its adjoint to obtain Hermitian terms. Vacuum-compress each assigned term using (3.24). Compression fixes the physical total D_q(a), so the resulting decomposition is still exact and now each term is physical. A monomial joining points at distance R is supported in B_{1+R}(x_1); the compression lemma bounds its approximation norm of order D by C_D(1+R)^{D+2}. The slot count (3.6), the tempered ratios, and K>D+\kappa+6 therefore make the assigned absolute sum converge with the required Dth moment. The stated value of K_D more than covers these losses and the fixed finite differences of the windows. The grade and reality are preserved by compression. Every step is linear before pairing adjoints, which also proves the difference assertion.
We record explicitly how the symbol criterion applies after subtracting an affine function. Let \rho(j,m) denote meridional distance between the latitudes of indices j,m, and fix a center x at index m. Suppose there are \beta>0, \kappa\geq0, and constants C_k such that, for every k\geq2 and j\in[0,q],
Define \widetilde a_x(j)=a(j)-a(m)-a'(m)(j-m). Taylor’s formula and (3.2) imply
Here is the bound for the two orders not already present in (3.31). The index excursion between m and j is at most a constant times w_q(j)(1+\rho(j,m))^2, and the ratio of w_q(j) to the minimum of w_q on that meridian segment is polynomially bounded by (1+\rho(j,m))^2. Integrating a'' once or twice therefore bounds w_q(j)|\widetilde a_x'(j)| and |\widetilde a_x(j)| by the right side of (3.32). On each window the widths are comparable and meridional distance changes by a bounded amount, proving the displayed seminorm bound.
Lemma 3.11 and the weighted commutator estimate now show that [D_q(\widetilde a_x),O_x] has rapid local size C\beta whenever O_x has bounded rapid local norms at x. In applications one can take \beta comparable to w_q(m)^2|a''(m)| and verify (3.31) directly. For an annular sum commuting with \mathcal N and \sum_jj c_j^*c_j, replacing a by \widetilde a_x leaves the commutator unchanged: the removed operator is a linear combination of those two conserved quantities.
Commutators, evolution, and spectral functions of physical operators remain physical, and neutral evolution preserves number grade. The strictly supported approximants used to measure locality need not preserve the vacant-complement subspace; physical vacuum compression is available when a physical representative is required. The frame may therefore be fixed while proving an operator estimate, changed when rotating an observable, or chosen compatibly at nearby fluxes. Lemmas 3.7 and 3.8 ensure that the same local estimates remain available after the spectral transports used next.
4 Pinning zeros and transporting weighted observables
We compare zero modes at fluxes differing by one or three. Multiplication by a zero at the south pole gives the algebraic comparison, but is not unitary. We construct a unitary comparison whose effect on a local observable is small away from that pole. For a convex orbital weight we also retain a sign in this comparison. That sign will be used in the first charge estimate in Section 6.
Fix d\in\{1,3\} and put t=q-d. The identification of orbital labels 0,\ldots,t embeds U_t isometrically into U_q; write \iota_{q,d} for its exterior-algebra extension. Its image has the last d orbitals empty. Set
Multiplication of a polynomial by the d south-pole zero factors, one factor for each particle, is \iota_{q,d}\exp D_t(g_{q,d}), up to a scalar on each number sector. In particular, the subspace of Z_{n,q} having these zeros is
Throughout this section, m, u=1+m, v=1+q-m, and w=(uv/(q+1))^{1/2} use the larger flux q. Replacing q by t in these size functions changes them by bounded factors. For every integer \ell\ge1, the smooth extension of Equation (4.1) satisfies, for 0\le m\le t,
Here and below constants can depend on d and on a stated differentiation or localization order, but not on q, n, or m.
4.1 A uniformly gapped path
For 1\le b\le2t-1, let B_{t,b} be the normalized pair annihilator whose coefficient at i<j, i+j=b, is proportional to (j-i)\sqrt{\binom ti\binom tj}. For 0\le s\le1 define
and
All these operators act on \mathcal F_t. Direct conjugation of each annihilator gives
The normalization in Equation (4.4) only multiplies each row by a positive scalar and therefore does not affect this identity.
Lemma 4.1 (Gap along the pinning path). There exist q_{\mathrm{pin}} and \gamma_{\mathrm{pin}}>0 such that
on the entire Fock space \mathcal F_{q-d}.
Proof. Fix an allowed unperturbed Fock gap \gamma>0. We compare columns of annihilators, rather than Hamiltonians. This avoids a factor equal to the number of particles.
Choose a smooth function \ell_B(x) on x\ge1, constant for x\le B, equal to \log x for x\ge2B, and with |\ell_B^{(k)}(x)|\le C_k(B+x)^{-k} for k\ge1. Replace each logarithm \log(q-j-r) in Equation (4.1) by \ell_B(q-j-r), retaining its constant denominator term, and denote the result by \bar g. Let \bar B_b(s) be the corresponding normalized rows. At m=b/2, the pair-row moment bounds of Lemma 3.10 imply
Here is the normalization detail in this application. Subtract the affine Taylor polynomial of \bar g at m from each of its two arguments. The subtracted contribution is constant on i+j=b and cancels in row normalization. Write z=|i-m|/w. Taylor’s formula, the derivative bounds on \ell_B, and w^2\le v give a bound Cw^2(v+B)^{-2}(1+z)^K for the remaining exponent; exponentiating costs at most another fixed power of 1+z. To check this also outside |i-m|\le(v+B)/2, observe that this exterior region has z\ge c\sqrt v whenever v\ge B, whereas logarithmic differences are bounded by C\log(1+v/B). If v<B, all the logarithms have bounded scaled derivatives on the whole row. Thus the elementary inequality |e^x-1|\le |x|e^{|x|} and the row moment estimates give both an \ell^2 coefficient error Cw^2/(v+B)^2 and an \ell^1 error C\sqrt w\,w^2/(v+B)^2. The normalization factor differs from one by the first of these errors. Since w^2/(v+B)^2\le C/B, it is bounded away from zero when B is large. Finally \|\sum e_{ij}c_jc_i\|\le\sum|e_{ij}| proves Equation (4.6).
Let \mathcal C_0\psi=(B_{t,b}\psi)_b and \bar{\mathcal C}_s\psi=(\bar B_b(s)\psi)_b. These are operators from \mathcal F_t to a direct sum of copies of \mathcal F_t. Equation (4.6) gives
The middle inequality uses w_b^2\le v_b and the spacing 1/2 of v_b. Consequently the operator-column error is at most CB^{-1/4}. Choose B, independent of q and s, so that this is at most \sqrt\gamma/2. Equation (4.5), also valid for \bar g, shows that the two columns have the same nullity in each number sector. The min–max principle for singular values and the supplied Fock gap therefore give
It remains to remove the rounding. Put \delta=g_{q,d}-\bar g and S_s=e^{sD_t(\delta)}. At most 2B+d orbital entries of \delta are nonzero, and each is bounded in modulus by C_d\log(2B). Thus
uniformly on the entire Fock space. If \mathcal C_s is the column of the unrounded normalized rows, row normalization gives
where R_s is diagonal in the row index. Since \ker\mathcal C_s=S_s\ker\bar{\mathcal C}_s, the preceding distance estimate implies
Squaring proves the assertion. The flux threshold only has to ensure t\ge q_\gamma and q\ge4B+d.
4.2 Local transport and comparison of consecutive fluxes
For the remainder of this section all compared path fluxes are assumed to be at least q_{\mathrm{pin}}. Taking q\ge q_{\mathrm{pin}}+6 ensures this for the comparisons of size at most three and the growth steps used below. Larger fixed comparison ranges require only a corresponding fixed increase in this margin.
We compare different orbital dimensions by a fixed convention. If t\le t', identify orbitals with the same labels and extend an even operator A on \mathcal F_t to A\otimes I on \mathcal F_{t'}, using the graded tensor decomposition over the additional modes. Its original matrix elements are recovered by putting those modes in the vacuum. We then use the common slot frames of Lemma 3.2. All operator differences below use this padding convention.
The local rate of the transport will be
In the north this rate is of order (1+m)/q^2; changing the flux by a bounded amount will gain one more inverse power of v.
Proposition 4.2 (Transport of the pinned spaces). There is a number-preserving and axially invariant unitary path U_{q,d}(s) on \mathcal F_t, starting at the identity, such that
Writing \partial_sU_{q,d}(s)=Y_{q,d}(s)U_{q,d}(s), the anti-Hermitian generator Y_{q,d}(s) is a rapid interaction of size C\alpha_q(m). In common frames, a bounded change in q, with d fixed, changes the generator interaction by size C\alpha_q(m)/v.
Proof. We first prove uniform row regularity and its flux difference, then estimate the affine-subtracted commutator that enters the spectral filter.
Row regularity. The unnormalized coefficients in Equation (4.4) are
They obey the pair-row bounds in Lemma 3.10 uniformly for 0\le s\le1. We give the normalization argument because the normalization is now a sum with moving endpoints. Write z=i-m. Relative to the undeformed row, after canceling its midpoint value, the additional factor is exactly
When v is bounded, all allowed z and w are bounded and the estimates follow from finite differences. When v is large and |z|\le c v, the logarithm of this factor and its derivatives in scale-w variables are bounded by C(w^2/v^2) times fixed polynomials in |z|/w. The positive exponential factor can be absorbed into half the Gaussian decay of the undeformed row, since its exponent is O(z^2/v^2) while that decay has exponent -c z^2/w^2 and w^2\le v. For |z|>c v, the factor in Equation (4.9) is at most C v^{d/2}, whereas |z|/w\ge c\sqrt v. The Gaussian tail therefore pays this factor and every required inverse power of w.
To control normalization differences, first retain a smooth central cutoff supported in |z|\le c\min(u,v) and equal to one on a smaller such interval. Use the smooth log-gamma expression for the undeformed row before normalization, and sum its square times E_s^2 and this cutoff over all fixed integers i. This is a smooth function of real m, bounded below by c w^3 after extracting the common midpoint binomial factor: the O(w) indices with |i-m|\asymp w contribute \asymp w^2 each. Its derivative of order k is at most C_k w^{3-k}, by the Gaussian moment bounds. The discarded tail is O_D(w^{3-D}) for every D, also after any fixed finite difference: bound that difference by its finitely many values at adjacent centers, where the scales are comparable. The chain rule for the retained positive normalization, followed by this tail estimate, proves the full finite-difference estimates for the exactly normalized rows. For bounded w the normalization is bounded above and below directly. Thus no derivative of a moving-endpoint sum is being assumed. Lemma 3.10 now proves that H_{q,d}(s) is a rapid interaction of bounded strength.
Flux differences. Use common windows for fluxes a bounded distance apart, as in Lemma 3.2. With orbital labels fixed from the north, their Hamiltonian interactions differ by size C/v. Indeed
For the path profiles, after canceling their common midpoint values, the corresponding ratio is exactly
Its difference from one has size Cw^2/v^2\le C/v in the row-symbol bounds. The preceding central-cutoff normalization argument, applied to the difference of the two profiles, retains this extra factor in every finite-difference bound. In using that argument, the factor w^2/v^2 is retained throughout |z|\le cv, including the part discarded by the smaller central cutoff. Only on |z|>cv is it recovered from tail powers, using v^2/w^2\le C(|z|/w)^2. This distinction is necessary when v is much larger than u. If an individual pair coefficient is present only at the larger flux, its index excursion satisfies |i-m|\ge v-O(1). For large v its Gaussian tail pays both the inverse of w^2/v^2 and every required symbol seminorm; for bounded v it is a bounded-scale estimate. The entirely new rows lie in a bounded south zone, where 1/v is bounded below. This proves the claimed common-frame interaction difference, including the changed endpoint supports. Repeating the one-flux identity handles any fixed bounded change in flux.
Affine subtraction. For a smooth real function a on the orbital interval, set X_a=[H_{q,d}(s),D_t(a)]. Decompose the Hamiltonian into annuli by a sum-of-squares partition \sum_k\vartheta_k(b)^2=1, of row-index width comparable to w_k, and then use its Fourier wavepackets. If m_k is the annulus center, put
The affine contribution commutes with the annular sum, because every row has a fixed pair index sum. More explicitly, if C_x is its Fourier wavepacket and C_x(a) is the same wavepacket with row coefficients multiplied by a_k^\circ(i)+a_k^\circ(j), then
The center measure has bounded mass in unit balls. The wavepacket normalization is w_k^{-1/2} and its circle measure is w_k\,d\phi/(2\pi), so Fourier orthogonality proves Equation (4.10) exactly. The weighted row bounds give size Cw^2|a''(m)| whenever Equation (3.31) holds with \beta=w^2|a''(m)|. For a=g_{q,d} this size is C\alpha_q(m): for every k\ge2,
and \alpha_q has tempered ratio exponent four, independently of k. Upon changing q by a bounded amount, the source interaction changes by size C\alpha_q/v: differences of g'' gain v^{-1}, and the row wavepackets change by C/v. These assertions include every fixed rapid localization order, since the estimates just used also apply after the finite differences used in Fourier localization.
Spectral filter. We use the spectral-filter construction of quasi-adiabatic continuation [6, 2], with locality supplied by Section 3. Choose a smooth odd real function \eta that is zero on [-\gamma_{\mathrm{pin}}/2,\gamma_{\mathrm{pin}}/2] and equals \operatorname{sgn}(\omega) for |\omega|\ge\gamma_{\mathrm{pin}}. Let r(\omega)=\eta(\omega)/\omega, with value zero near zero, and use the spectral calculus of \operatorname{ad}_{H}(A)=[H,A] to set
The function r and each of its derivatives belong to L^2(\mathbb R). Its inverse Fourier transform therefore has every absolute polynomial moment: use Cauchy–Schwarz on |t|\le1, and the L^2 norm of a sufficiently high derivative of r on |t|>1. Lemma 3.7 and Equation (4.10) give rapid locality with size \alpha_q.
The spectral multiplier of D_t(g) is \eta(\omega), so Y^*=-Y. If P=P_{q,d}(s) and Q=1-P, the gap gives
Differentiating Equation (4.5) gives \partial_sP=QD_t(g)P+PD_t(g)Q=[Y,P]. The unitary solution therefore transports P. Both H_{q,d}(s) and D_t(g) commute with number and with \sum_jj c_j^*c_j, proving the two symmetries.
Finally compare two fluxes in common frames. The change of X_g has size \alpha_q/v. The Hamiltonian change has size 1/v. Inserting the latter into the time evolution in the filter by Duhamel’s formula costs \alpha_q/v, by Lemma 3.8. All filters are the same for every flux and every path parameter. This proves the difference assertion.
The isometry used subsequently is \mathcal U_{q,d}=\iota_{q,d}U_{q,d}(1) restricted to Z_{n,q-d}. By Equation (4.2), its image is exactly the subspace with d south-pole zeros.
Corollary 4.3 (A fixed observable in the northern region). Let O be a neutral operator of norm at most one supported on B_r(x), where r\ge2 and x has latitude index m. There are fixed constants b,C_*, and c=8, independent of every tail order below, such that, if q>Cr^b(1+m), the operator
satisfies
In particular, it admits a decomposition
For |q-q'|\le3, with the same d and identical northern slots, \Delta_{q,d}(O)-\Delta_{q',d}(O) obeys all these estimates with q^{-2} replaced by q^{-3}. In particular, for every fixed B, the shell decomposition can be chosen so that
and the same moment estimate holds for the flux difference with q^{-3}.
Proof. At the center the cutoff gives v\asymp q, so \alpha_q(m)\le C(1+m)/q^2 and \alpha_q(m)/v(m)\le C(1+m)/q^3. Use the supported-observable bounds in Lemma 3.8, first for the self-adjoint path generators iY_{q,d}(s) and 0. Since \alpha_q=u/((q+1)v), its tempered ratio exponent can be taken to be four: each of u and v^{-1} costs at most two powers of distance. Equations (3.22)–(3.23) give a core factor r^6 and every tail order beyond radius Cr. Apply the same bounds directly to iY_{q,d}(s) and iY_{q',d}(s) for the comparison. Their difference has size \alpha_q/v=u/((q+1)v^2), whose ratio exponent is at most six, and therefore costs r^8. Thus c=8 suffices for both assertions. Choose b large enough that the initial ball uses identical northern slots. The common-frame generator comparison already includes the padded south modes, so this same bound covers the endpoint changes. Take the ball approximations by the normalized partial trace onto the corresponding slot algebra. This contraction has error at most twice the best approximation error and preserves number grade. Differences at radii C_*2^\nu r give one decomposition satisfying Equation (4.13) for all tail orders, after increasing C_* by one fixed factor. Choose the tail order greater than B+1 and sum the resulting geometric series to obtain Equation (4.14).
4.3 Convex weighted observables
For fixed 0<p<2 and L\ge2, put
Constants in the next statements can depend on p, but are uniform in L\ge2. Direct calculation gives
We use d\mu for the center measure above; its integral of a radial tempered size is bounded by a constant times \int_0^t(\cdot)\,dm. These weights satisfy the precise symbol hypothesis needed for affine subtraction. For every k\ge2,
The ratios of \beta_q(j) have a fixed polynomial bound in meridional distance, independent of k and L\ge2. Thus Equation (3.31) applies with \beta=\beta_q(m) at each chosen center.
Proposition 4.4 (Change of a weighted number observable). The operator
has a rapid interaction representation of size CA_q(m). Its interaction difference under a bounded change in q, with d fixed, has size CA_q(m)/v in common frames. The pieces may be assigned to their original annular centers throughout the construction.
Proof. Retain the annular decomposition of Y used in its construction. Each annular total commutes with number and axial angular momentum: this is true of its source in Equation (4.10) and remains true under the time filter. We may consequently replace f(j), in its commutator with this annular total, by f(j)-f(m_k)-f'(m_k)(j-m_k). Lemma 3.11 bounds the resulting one-body interaction near the annulus by C\beta_q; its bounds away from the center grow only polynomially with distance. The weighted commutator calculus thus bounds [D_t(f),Y(s)] by C\alpha_q\beta_q. Integrating
proves the first assertion. For the difference, use the same padded D(f) on both systems: its additional end-orbital number operators commute with the smaller system’s generator. Thus no uncompensated end value of f occurs. The source and generator differences supply the factor v^{-1} proved above; the difference of the transporting evolutions supplies the same factor by Duhamel’s formula. The weights A_q and v^{-1} have uniformly polynomial ratios, so Lemma 3.8 applies also to their product. All decompositions start with an annular source and expand its evolved operator in shells about that source. This gives the last assertion.
The preceding norm estimate costs C\int A_q(m)\,dm. Summation over successive fluxes requires the stronger one-sided estimate below. The weight f is convex whereas the pinning logarithm g is concave. Their affine-subtracted quadratic parts therefore have opposite signs. After filtering, these leading parts form a negative square; the cubic Taylor remainder costs the additional factor 1/w.
Proposition 4.5 (One-sided change in a zero space). Writing P_0 for the zero projection of H_t, one has
Proof. Fix s and abbreviate H=H_{q,d}(s) and P=P_{q,d}(s). The derivative in the transported zero space is the compression of
We estimate this operator before integrating in s.
Choose a smooth \chi_+ equal to zero for \omega\le\gamma_{\mathrm{pin}}/2 and to one for \omega\ge\gamma_{\mathrm{pin}}. Apply the filter r_+(\omega)=\chi_+(\omega)/\omega separately to the pieces in Equation (4.10), and set
As in the preceding filter argument, its time kernel has all absolute polynomial moments. Every piece has strictly positive spectral frequencies. Thus
At a center of latitude index m, put \rho_x=f''(m)/(-g''(m))>0. The common wavepacket decomposition gives
where G_x has size C\alpha_q(m) and E_x has size C\beta_q(m)/w(m), at every fixed rapid order. We verify the improved error explicitly. The function a=f+\rho_x g has a''(m)=0. Subtract its affine Taylor polynomial, as in Equation (4.10). In a row window of width w, the third-order remainder is bounded, with all scaled derivatives and polynomially weighted tails, by
The last inequality uses w^2\le u,v and u\le L+m. For windows outside this central region, derivative ratios have polynomial growth and the row tails absorb those powers. The weighted row estimate applied to C_x(a) proves the claimed source error; the same time filter preserves it. This proves Equation (4.19) without making any assertion about the sign of individual unfiltered row pieces.
Write R_g=\int G_x\,d\mu(x), R_f=\int F_x\,d\mu(x) and T=\int\sqrt{\rho_x}G_x\,d\mu(x). Each integral is finite at fixed flux. From Equation (4.18), a reversed product with a raising operator on the left vanishes in the compression, giving PG_x^*G_yP=P[G_x^*,G_y]P. Expanding Equation (4.19) therefore gives the exact identity
We give the norm bounds for the last two integrals, since their spatial summability is essential. If D=\operatorname{dist}(x,y), rapid localization and the even parity of the pieces imply, for every fixed M,
Here subscripts denote evaluation at the corresponding center. The logarithmic derivative of \rho is bounded by C((L+m)^{-1}+v^{-1}). Using radial resolution w and the polynomial ratio bounds of Section 3 consequently gives a fixed exponent k such that
This bound follows by integrating the logarithmic derivative along the meridian between the two latitudes when the distance is at most a small multiple of w_x; outside that region its right side dominates the polynomial ratio bound after increasing k. Since \rho_x\alpha_x^2\asymp A_x, choose M above all these polynomial exponents plus the two-dimensional volume exponent. Summing first in y bounds the second line of Equation (4.20) by C\int A_x/w_x^2\,d\mu(x), and its third line by C\int A_x/w_x\,d\mu(x). Since w\ge1 and -2PT^*TP\le0, Equation (4.17) is at most C\int_0^t A_q(m)/w(m)\,dm in quadratic form. Conjugate back by U_{q,d}(s) and integrate over 0\le s\le1 to obtain Equation (4.16).
Corollary 4.6 (Cost of changing a calibration state). Let q^0=3\lfloor q/3\rfloor and r=q-q^0\in\{0,1,2\}. Consider the interaction K_{q,3}(f) on \mathcal F_{q-3} and its common-frame comparison with K_{q^0,3}(f). Embed a unit vector \xi\in Z_{n,q^0-3} by the common orbital labels, or instead grow it to flux q-3 using the r isometries \mathcal U_{Q,1}. The following costs are each bounded by
the change of interaction in the embedded state, and the change of its expectation between the embedded and grown states. The same bounds hold after selecting any common collection of source-center pieces, and after adding their absolute bounds. In particular the statement applies to the filled vector at flux q^0-3 and to separate northern and southern portions of the interaction.
Proof. The first assertion is the integrated interaction difference in Proposition 4.4; vacant extra modes are compressed after comparison in the common frame. For one growth step, differentiate the expectation of the interaction along U_{Q,1}(s). The generator has size \alpha_Q\le C/v, while the observable interaction has size A_q. The weighted commutator calculus bounds the derivative in operator norm by C\int A_q/v. Finite-parameter conjugation preserves this bound. There are at most two growth steps, and all size functions for their fluxes are comparable. Applying this argument to each selected source piece before summing proves the last assertion, including comparisons with the directly embedded lower-flux reference on common northern slots.
5 Reading zero modes by orthogonal branches
We now turn the pinning maps into coordinates on every zero space. At each step we either record a hole or remove an electron. The coordinates are orthogonal, although the holes themselves have not been assigned positions. The purpose of the construction is quantitative: a local observable near the north pole can change substantially only when the coordinates record a hole sufficiently far along the descent toward that pole. We prove this assertion as an operator inequality, and then use rotation averaging to obtain a uniform comparison in the one-hole spaces.
Throughout this section, all lower bounds on the flux are absorbed into one fixed integer q_{\mathrm{stop}}\geq 4. We stop every descent when q\leq q_{\mathrm{stop}}. Constants may depend on this stopping value, on the uniform constants of the local calculus, and on a fixed decay exponent. They never depend on q or on the particle number.
5.1 The algebraic decomposition
Let P_q be the orthogonal projection onto the Fock zero space Z_q=\bigoplus_n Z_{n,q}. Write n_q=c_q^*c_q for occupation of the south-pole orbital. In a nonzero sector Z_{n,q} set
For n\geq 1, divisibility by the cube of every pair determinant gives
Thus h\geq0. We retain Equation (5.1) also in the vacuum sector, where h=q+3.
Denote by Z_{n,q}^{(d)} the subspace in which each electron has d zeros at the south pole. The endpoint transport from Section 4, followed by the inclusion with its last d orbitals vacant, will be denoted by
It is an isometry, preserves particle number and the sum of the orbital indices, and is defined with the same choices on all number sectors.
Lemma 5.1 (Two orthogonal branches). For q>q_{\mathrm{stop}}, define
Then \mathcal F_{n,q}=Z_{n,q}^{(1)}. Contraction by c_q maps \mathcal E_{n,q} bijectively onto Z_{n-1,q}^{(3)}. If \mathsf T_q denotes the polar part of c_q|_{Z_q}, the maps
are isometries onto the two orthogonal branches. Consequently,
The second summand is absent for n=0. In the first summand h decreases by one; in the second it is unchanged.
Proof. The absence of orbital q is equivalent to divisibility by the north spinor coordinate in every variable, which is precisely one pin at the south pole. Evaluation of one electron at that pole leaves the three pair zeros attached to every remaining electron. This proves that the range of c_q lies in Z_{n-1,q}^{(3)}.
To prove surjectivity, use the affine coordinate in which the south-pole coefficient is the coefficient of the highest power. After factoring the Laughlin polynomial, the map on symmetric polynomials extracts the coefficient of z_n^h. A basis of its target consists of monomial symmetric functions indexed by partitions with at most n-1 parts, all at most h. Append a part equal to h and take the corresponding monomial symmetric function in n variables, with each distinct monomial included once. Extraction returns the original monomial symmetric function. This proves surjectivity, including h=0. Restriction to the orthogonal complement of the kernel is therefore bijective, and its polar part is unitary onto the range. Composing with the endpoint transports gives the stated isometries. The assertions about h follow directly from (5.1).
Figure 2 displays the changes in flux, particle number, and hole number in the two branches.
Figure 2: One step of the orthogonal decomposition. The displayed spaces are coordinate spaces for the two branches. A flag is a record of an F step; it is not a measured position of a quasihole.
The remaining issue in this decomposition is analytic. A polar decomposition need not be local when its nonzero singular values approach zero. The next lemma rules out that problem uniformly in the flux.
5.2 A local polar map
Lemma 5.2 (Occupation gap and local representatives). There is \varepsilon>0, independent of q and of the number sector, such that
The polar map \mathsf T_q and the projections onto the two branches, restricted to Z_q, have bounded physical representatives rapidly localized at the south pole. The representatives preserve Z_q and its orthogonal complement. They have respectively the number and index grades of c_q and of the identity.
Proof. We first prove the singular-value bound, keeping track of the restriction of pair rows. The normalized rows are
For completeness, their normalization follows by taking coefficients in
If a row contains orbital q, put k=2q-b. Its removed coefficient mass is
Here p_{q,1}=p_{q,2}=1, and
It follows that every row with a retained pair has retained mass
Rows with no coefficient at q have mass one. The two top rows retain no pair and are omitted.
For d=1, the pinning weights obey g_j=\tfrac12\log((q-j)/q). Multiplication of its coefficients by e^{-g_i-g_j}, followed by normalization, turns a flux-(q-1) row into the normalized retained flux-q row. More precisely, if B_{q,b}^{\mathrm{ret}} denotes the row with the coefficient at orbital q deleted, then B_{q,b}^{\mathrm{ret}}=\sqrt{r_{q,b}}B_{q,1,b}(1), in the notation of Equation (4.4). Let \delta>0 be the uniform endpoint gap from Lemma 4.1. By (5.5), the Hamiltonian compressed to the south-empty sector has a gap at least \delta/4 above \bigoplus_n\mathcal F_{n,q}.
The CAR give the exact identity
The coefficient sum is
One way to see this is to write p_{q,k}=k\binom{2q-k-1}{q-1}/\binom{2q-2}{q-1} and apply the hockey-stick identity twice. For \psi\in Z_q, the two top singleton rows also imply c_{q-1}c_q\psi=c_{q-2}c_q\psi=0. Hence
Let Q=1-n_q and let P_F project onto \bigoplus_n\mathcal F_{n,q}. Since B_{q,b}\psi=0, the restricted gap gives
The occupied and vacant components are orthogonal, so
Thus (5.4) holds with \varepsilon=\delta/(\delta+8).
To construct local representatives, take a real smooth frequency cutoff \chi equal to one near zero and supported strictly inside the uniform unperturbed gap. Apply its time filter to c_q:
with the Fourier normalization incorporated into \widehat\chi. Contraction preserves zero modes. The cutoff therefore gives A_qP_q=c_qP_q and [A_q,P_q]=0. The local calculus makes A_q rapidly localized at the south pole, with uniform constants. Choose a smooth function \eta on a fixed interval containing the spectrum of A_q^*A_q, equal to zero near zero and to x^{-1/2} for x\geq\varepsilon. Then
is rapidly localized by smooth functional calculus and agrees with \mathsf T_q on Z_q. Its products \widetilde{\mathsf T}_q^*\widetilde{\mathsf T}_q and 1-\widetilde{\mathsf T}_q^*\widetilde{\mathsf T}_q represent the branch projections on Z_q. The construction preserves number and index grades because H_q preserves both and A_q^*A_q has grade zero. It also preserves P_q in both directions. No claim about a spectral gap of A_q^*A_q outside Z_q is needed: \eta is smooth on that entire spectral interval.
5.3 One-step comparisons
Write
on the corresponding smaller zero space. Proposition 4.4 supplies localized representatives for these operators, with the stated size and flux-comparison estimates.
Proposition 5.3 (Weighted observable at one branch). Fix p\in(0,2), L\geq2, and f(j)=f_{L,p}(j). In the orthogonal coordinates (5.3),
The notation in the left side means the unitary whose columns are the two branch isometries. The bound includes the off-diagonal blocks. For affine f the remainder is zero and K_{q,d}(f)=0.
Proof. The F block is the definition of K_{q,1}(f). For an affine sequence, the grades of \mathsf T_q give
on the zero spaces, and both branch projections commute with D_q(f). The endpoint transports commute with the number and index operators. This proves the affine assertion, including the scalar f(q) in E.
For a general f, subtract its affine Taylor polynomial at q. The remainder a(j)=f(j)-f(q)-f'(q)(j-q) satisfies
The same polynomial bounds hold for the finite differences needed for localization. In the south-pole frame this says that D_q(a) has one-body interaction size at most C_pf(q)/(L+q)^2, times a fixed polynomial in distance from the pole. Commuting it with any of the rapidly localized representatives in Lemma 5.2 thus has norm at most that size: decompose the representative into ball shells and sum its arbitrarily high inverse-power tails against this polynomial. In the E block use \mathsf T_q[D_q(a),\mathsf T_q^*]; for the off-diagonal blocks use the commutator with a branch projection. Compression and the endpoint isometries do not increase these norms. This proves (5.7).
For a general observable supported far to the north, the polar map contributes an even smaller error, because its representative is localized at the opposite pole. We record the precise form used below.
Lemma 5.4 (Northern comparison). There are fixed c\geq0 and b_0\geq1 with the following property. Let O=O^* be neutral, of norm at most one, supported on a slot ball of radius r\geq2 centered at latitude index m, and put u=1+m. If q>C r^{b_0}u, identify all northern slots in the fluxes being compared. The two diagonal branch blocks of O equal
up to a matrix remainder of norm C_Dq^{-D} for every fixed D. Each \mathcal D_{q,d}(O) is neutral and self-adjoint. If x is its original center, then, for fixed c,C_*<\infty and every D>0,
For |q-q'|\leq2 and fixed d, the difference between these changes, in common northern slots, obeys the same two estimates with q^{-2} replaced by q^{-3}. The exponent c and core constant C_* are independent of D.
Proof. For F, this is Corollary 4.3. Its norm and tail estimates are Equations (4.11) and (4.12); enlarge the fixed core constant to write the outer ball radius as R instead of r+R. For E, commute O through the local representative of \mathsf T_q before applying that corollary with d=3. The support of O is a distance comparable with \sqrt q from the south pole when b_0 is increased if necessary. Rapid locality therefore makes the polar commutator and the off-branch blocks O(q^{-D}) for every D. The same estimate handles the finitely many trimmed orbitals. The difference assertion for the remaining changes is the same-corollary comparison of the pinning transports at bounded flux difference.
5.4 Histories and a linear reference expectation
Iterate the two branch coordinates until the flux reaches q_{\mathrm{stop}}. A word \omega records its successive F and E choices; its terminal number and flux are denoted by n_\omega and q_\omega. The resulting unitary is
For a fixed readout axis and fixed filters, the maps J_{q,F}, J_{q,E}, and \mathcal R_{n,q} are defined on physical Fock spaces independently of the auxiliary slot frames. Rebuilding frames outside the common northern slots changes only the representations used to prove locality estimates; it does not redefine these maps or their history coordinates. An F step taken at flux b records one flag with value b. At a terminal space we add q_\omega+3-3n_\omega flags, all with value zero. Let \mathcal B(\omega) be this multiset. Each word has exactly h flags. The vacuum follows only F steps, with the same terminal convention. We do not resolve the bounded-dimensional terminal space further.
Fix a\in(0,2). On the direct sum in (5.9), define the positive diagonal operator
Its value is scalar on each terminal summand. In particular W_m=0 on the filled zero space, and W_m\geq(1+q)^{-a} whenever h>0.
We next fix the scalar used to center observables. Put q^0=3\lfloor q/3\rfloor, and let \Omega_{q^0} be the normalized filled zero mode at that flux. Embed its one-particle space into U_q by sending orbital j to orbital j, and then use the slot embedding at flux q, with the orthogonal complement of the embedded one-particle space vacant. Define
in this padded realization. This is a positive linear functional of norm one on the slot algebra. At q=q^0 it is the filled expectation. For q^0=0 the convention is U_0=\mathbb C with its unique normalized one-electron filled vector. Outside the common northern region only linearity, the norm-one bound, and the exact filled expectation at q=q^0 will be used.
Lemma 5.5 (Compatibility of reference expectations). Let two fluxes q,q' use common northern slots, and let s\leq\min(q,q'). Embed a fixed vector of \mathcal F_s into either system by the same orbital labels, with the orthogonal complement of the embedded one-particle space vacant. The two states have identical expectations on the algebra of common northern slots. In particular, references at fluxes with the same nearest lower filled flux agree on that algebra.
Proof. Expand a slot observable into normally ordered CAR monomials. Its expectation in an embedded state is a linear combination of the state’s normally ordered orbital correlations. The coefficients use only the analysis-frame entries of the slots occurring in the monomial. Entries at orbital labels above s contribute zero, because those orbitals are vacant. At labels at most s, the common northern frame entries are identical. Thus every monomial has the same expectation in both realizations. This also proves the assertion after physical compression of the slot observable, which leaves these matrix elements unchanged.
The parent and its E child use filled states at q^0 and q^0-3, respectively. Their expectations are related by the filled E step. By contrast, the references at q-3 and q^0-3 use the same filled state and agree on common northern slots by Lemma 5.5. For a rapidly localized operator, apply this exact identity to a truncation supported in those slots; the remaining difference is at most twice the truncation error. The common-frame construction permits these conventions for every frame entering a comparison, with uniform estimates.
Theorem 5.6 (Local observables in history coordinates). For every fixed a\in(0,2) there are B,C<\infty such that the following holds uniformly in n,q and in the allowed slot frames. Let O=O^* be a neutral slot observable of norm at most one, supported in a ball of radius r\geq2 with center of latitude index m. Its compression to Z_{n,q} satisfies
Here P_{n,q} denotes the zero-space projection in the number-n sector. More generally, for a convergent decomposition A=\sum_\nu A_\nu into neutral self-adjoint observables supported in balls about the same center, of respective radii r_\nu\geq2, the right side can be replaced by CW_m\sum_\nu r_\nu^B\|A_\nu\|.
Proof. The proof keeps O unchanged while descending through common northern slots. Only the small changes caused by each transport are estimated inductively. This distinction prevents an increasing radius from being assigned repeatedly to the original observable.
We first describe the centered one-step identities under the northern condition of Lemma 5.4. For an E step put t=q-3, so t^0=q^0-3, and write R_{q,E}(O) for its uncentered polar remainder in Lemma 5.4. The filled E step at q^0, together with compatibility of the northern references, gives the exact scalar identity
Thus the parent-to-child reference change is determined by a filled step. Define
The references in the second line use the same filled state. Lemma 5.5, first on common northern slots and then on rapid tails by norm approximation, therefore gives
The bounded-flux comparison in Lemma 5.4 supplies the additional factor q^{-1}. Substituting these scalar identities into the branch comparison yields
Here and below the symbols denote compressions to the relevant child zero space. When h=0 the comparison is its own filled calibration, so all centered contributions vanish exactly.
For an F step, t=q-1. The nearest smaller filled fluxes are either identical or differ by three. In the latter case apply the filled E comparison just used. Together with (5.8), this proves
The off-diagonal blocks have norm C_Dq^{-D}. An F step already records a flag, so its entire error will be charged to that flag.
Here is a uniform closure argument, including the parameter choices. Let c,b_0 be as in Lemma 5.4. Choose b>\max\{b_0,c\}, then choose B>\max\{ab,c\} large enough to absorb the fixed polynomial costs of the local calculus. A constant M will be fixed after B. Set
If q\leq\tau and h>0, every flag has b'\leq q, so
The norm bound \|O-\operatorname{ref}_q(O)\|\leq2 proves (5.12) in this region with constant 2(2M)^a. When h=0 the centered compression is zero. Increasing M includes all stopping cases in this argument.
Fix a finite Q, and let K_Q be the least constant in (5.12) for fluxes at most Q, with the chosen B, all number sectors, and all allowed frames. This number is finite: for h>0 use W_m\geq(1+Q)^{-a}, while the filled compression is exactly centered. We prove
with C_M independent of Q.
Suppose q>\tau. Expand the unchanged O down the branching tree, using (5.13) and (5.14), until the current flux is at most \tau. The original northern slots, center, and radius are unchanged through this part of the descent. The terminal comparisons have just been bounded. In an E child, decompose \mathcal D_{q,3}(O) into its core and dyadic ball shells, all centered at m. Equation (4.14), with a tail order larger than B+2, gives
Applying the definition of K_Q to each smaller-flux shell, and using linearity of the reference, bounds its centered contribution by
times the remaining history weight in that child. Along any word, the flux strictly decreases; thus
Consequently all induction-dependent contributions are bounded by
Choose M so large that this is at most \tfrac12 K_Qr^BW_m. This choice is possible because b>c and r\geq2.
We verify that the other errors have a bound independent of K_Q. At a node with positive remaining hole number, its identity is bounded by the sum of the identities assigned to its remaining flags. A scalar electron error may therefore be charged to every such flag. For a flag at \ell, the total charge from ancestors in (5.13) is at most
The F error in (5.14) occurs at its own flag and obeys the same bound, up to a fixed constant. Write w_\ell=\min\{1,(u/(1+\ell))^a\}. Since a<2 and \tau=Mr^bu,
The q^{-D} remainders, including the off-diagonal blocks, obey the same estimate after choosing D>a+2. For a self-adjoint off-diagonal block, its norm bounds the full block matrix above and below by that norm times the identity at its node, so the same charge applies. Nodes with h=0 contribute nothing, by the exact centered filled identity. Summation of these diagonal bounds along words proves (5.15).
It follows that K_Q\leq2C_M for every Q, proving the uniform claim. Finally, the assertion for A=\sum_\nu A_\nu follows by linearity of the reference and by summing the form inequalities.
The theorem estimates a compression to the zero spaces. It does not claim that ordinary local fluctuations vanish in the filled state. It also applies to coherent superpositions of histories: all charges above are diagonal operator bounds, rather than bounds conditional on a classical choice of word.
5.5 Rotation averaging in a one-hole space
The history estimate still depends on a chosen readout axis. In this subsection, a one-hole space means a space with quasihole degree h=1. Representation theory then removes the axis dependence and yields an integrated estimate with no factor of the sphere area.
Corollary 5.7 (One-hole comparison). Suppose h=1, equivalently q=3n-2. Let \psi,\phi be any two unit vectors in Z_{n,q}. Let \{O_x\} be a measurable family of neutral self-adjoint observables of norm at most one, supported in balls of a fixed radius r\geq2 about x, with center measure of bounded density. There are constants C,B'<\infty, independent of n,q, such that
The same conclusion holds for rapidly localized families, with the right side bounded by the corresponding fixed rapid-locality seminorm. For a family whose norms are bounded by A, multiply the right side by A.
Proof. Choose a\in(1,2) in Theorem 5.6. The symmetric-polynomial factor in (5.2) has degree one in each variable. It is the irreducible spin-n/2 representation, so Z_{n,q} is irreducible and has dimension n+1.
When h=1, an F branch has h=0 and hence dimension one. Before that branch all steps are E, which lower the flux by three. Therefore at most one one-dimensional history has a flag at any specified nonterminal flux. The history that reaches the stopping region without an F step has bounded terminal dimension. It follows that, as an operator on Z_{n,q},
The trace is unchanged on conjugating back to the physical zero space. Write \widehat W_0=\mathcal R_{n,q}^*W_0\mathcal R_{n,q} for that physical operator.
Let V_q(g) denote the rotation representation, with normalized Haar measure dg. Schur’s lemma gives
For each rotation use the readout axis whose north pole is the image of the original north pole. Precisely, write x(g)=g\cdot\mathrm{north} and W^{g}=V_q(g)\widehat W_0V_q(g)^*. Use the rotated frame and rotated branch construction at x(g). Theorem 5.6, applied to O_{x(g)}, gives
The two reference expectations cancel in this inequality. Changes between local frames cost only a fixed polynomial in r by the local calculus. Integrating rotations and multiplying by the sphere area yields at most Cr^{B'}q\operatorname{Tr}(W_0)/(n+1), which is uniformly bounded because q=3n-2. For any center measure with bounded mass in unit balls, spread the mass at each center over a ball of fixed radius. The resulting density relative to area is bounded uniformly. The operator originally assigned to x is supported in a ball of radius r+1 about every point in that spreading ball, so the same pointwise bound applies before integration. This reduces the general center measure to the area estimate. Finally, summing ball shells proves the assertion for rapid families.
6 Charge bounds and rotation averaging
The history estimate of Theorem 5.6 controls a local observable by weighted flags. To treat arbitrary hole number by rotation averaging, we compare these weights with a physical one-body observable, first with a slowly decreasing weight and then with a summable weight.
Increase the fixed stopping flux in the history construction, if necessary, so that it is at least eight and all pinning comparisons above it are valid, including shifts by at most three. Write q_{\rm s}=q_{\mathrm{stop}} and let \mathcal R_{n,q} denote the history unitary in (5.9). For L\ge2 and 0<p<2, put
When q is divisible by three, C_q(f) is the filled-state expectation of D_q(f): rotational invariance gives occupation (q+3)/(3(q+1)) in every orbital. The formula defines the scalar C_q(f) also at the other fluxes. The operator S_{L,p} is diagonal in histories and scalar on each terminal summand. Its sum is over the flag multiset \mathcal B(\omega), including all terminal flags at position zero; each history has exactly h=q+3-3n flags. All operator inequalities involving S_{L,p} below are in history coordinates. In particular, they make no measurement assumption about flags in a zero-mode vector.
Proposition 6.1 (Pooled charge). For each of p=1/8 and p=3/2 there are fixed L\ge2 and c>0 such that, for every flux and every nonzero zero-mode space Z_{n,q},
Here compression to Z_{n,q} is understood, and P_{n,q} denotes its orthogonal projection. The constants are independent of q,n and of the readout axis. When h=0, both sides vanish.
The obstruction to this estimate occurs at electron steps. Along a history, each F step contributes approximately -f(q)/3 to D_q(f)-C_q(f)\mathbf1, supplying a credit for its new flag. Each E step contributes a positive scalar correction. When at least two flags remain, divide this scalar cost between them. The scalar tail estimate below leaves the strictly positive margin
With one remaining flag, there is no such margin. We instead combine the scalar with the transported observable and compare it to a filled step; the one-hole comparison of Corollary 5.7 makes the resulting error summably small. These two cases prove the first charge estimate.
Rotation averaging then bounds integrated local-expectation differences between two zero-mode states by C(q+1)^{7/8} times the sum of their hole numbers. This still grows with the area, but it is enough to prove the charge estimate again with p=3/2. For a polar annulus 1+m\asymp M, use this averaged bound while the flux is moderate relative to M; the transport interaction has a factor (q+1)^{-2} that pays for the area dependence. At larger flux, apply the original fixed-axis history estimate directly to the annulus. The two resulting sums are small when the new weight scale L is large. The summable weight then gives the area-independent local-expectation bound at the end of this section.
6.1 Scalar telescoping and summable error bounds
We estimate D_q(f)-C_q(f)\mathbf1 from above. An F step contributes the scalar C_{q-1}(f)-C_q(f), and an E step contributes
For the continuous comparison define
with the continuous extensions at zero.
Lemma 6.2 (Scalar estimates). Fix p\in(0,2) and a lower stopping flux q_{\rm s}\ge8. There is a function \varepsilon_p(L)\to0 as L\to\infty with the following properties, uniformly for q\ge q_{\rm s}:
The function \ell is nonnegative. If 0<p<1, then for every collection \mathcal E of E-step fluxes along a history, and every flag position k below these steps,
Changing k by a fixed bounded amount, or taking k in the terminal range, only changes \varepsilon_p(L).
Proof. The exact formula
is obtained by separating the last three summands in C_q. A useful positive form of this identity is obtained by putting d_j=f(j)-2f(j+1)+f(j+2) and Q_q=(q+1)(q-2):
Expanding the second differences verifies the formula coefficient by coefficient. In particular, \ell_q\ge0, and constant and affine functions contribute zero.
Here are precise discrete-to-continuous error bounds:
for r=0,1,2. We give details because the sharper second estimate is needed for the summable weight. The identity d_j=\int (1-|t-j-1|)_+f''(t)\,dt expresses (6.9) as \int_0^q \kappa_q(t)f''(t)\,dt. The function \kappa_q is linear between consecutive integers and has values
On [0,q-2] its difference from t^2/q^2 is at most C(t/q^2+t^2/q^3), and on [q-2,q] that difference is bounded by a constant. The error in its integral against f'' is consequently at most
For q\le L use f''\le C/L^2; for q>L use \int_0^q tf''\le1, \int_0^q t^2f''\le2qF(q), and f''(t)\le C f(t)(L+t)^{-2}. This proves the first term of (6.10). The continuous identity \ell(x)=x^{-2}\int_0^x t^2f''(t)\,dt implies \ell'(x)=f''(x)-2\ell(x)/x, which proves the oscillation estimate.
For (6.11), difference the positive formula directly:
The first sum is bounded by CqF(q), as follows by its integral representation and \int_0^q t^2f''\le2qF(q). This gives CF(q)/q^2 when q>L; the last two terms cost Cf(q)/q^2. Below L use d_j\le C/L^2 in the displayed formula. A bounded number of differences proves the claimed bound.
The exact F-step identity is
For q\le L its ratio to f(q) is O(L^{-1}). For q>L use
The resulting ratio is O(L^{-1}) also when 1<p<2, since L^{1-p}q^{p-2}\le L^{-1} for q\ge L. The case p=1 follows from the explicit logarithmic integral and is not needed below. Dividing (6.11) by f(q) and summing gives O(L^{-1}) below L. Above L it gives O(L^{-1}): the summands are O(q^{-2}) for p<1 and O(q^{-2}+L^{1-p}q^{p-3}) for 1<p<2.
Twice integrating f'' proves
The E-step intervals [q-3,q] have disjoint interiors along a history. Consequently their continuous contribution is at most \frac13\int_{(k-3)_+}^{\infty}\ell(x)\,dx. For p<1, (6.12) bounds this by \frac{1+p}{3(1-p)}f(k), up to O(L^{-1})f(k) from the bounded endpoint shift. Finally, the tail sum of (6.10) is bounded by C/(L+k), and
Thus it is O(L^{-1})f(k) uniformly in k. This proves (6.7).
We next list the analytic error sums that will be used in both charge arguments. Retain the size function A_q from Proposition 4.4. With u=1+m, v=1+q-m, and w=\sqrt{uv/(q+1)}, it satisfies
The longitude integral has bounded mass and is included in constants. Proposition 4.4 gives this size for each transported change in D(f).
Lemma 6.3 (Uniform error sums). For either p=1/8 or p=3/2, as L\to\infty,
For p=1/8 there are, in addition,
All implied constants are independent of L.
Proof. For q\le L, integrating u^2/L^2 gives B_q\le C(q+1)L^{-2}; for q>L, dropping the factor (u/(L+u))^2 gives B_q\le C F(q)/q. These estimates and (6.12) prove the first bound in (6.14). On the northern half of the sphere v\ge(q+1)/2, whereas on the southern half A_q(m)\le C f(q)(L+q)^{-2}. Therefore
The first term sums to O(L^{-1}): above L it is bounded by Cq^{-2} for p<1 and by CL^{1-p}q^{p-3} for p>1. The second sums to O((1+\log L)/L).
For the supremum in (6.15), use CL^{-2} when q\le L and C(q+1)^{-2} otherwise. The latter divided by f(q) is O(L^{-p}q^{p-2}), whose sum is O(L^{-1}) for p<1. On the northern half, w\ge c\sqrt u, so the last integral is at most
After division by f(q), both terms are bounded by C\sqrt{q+1}/L^2 for q\le L and by Cq^{-3/2} for q>L, provided p<1/2. Their sums are O(L^{-1/2}).
6.2 Calibration and the first charge estimate
Set K_q:=K_{q,3}(f) on \mathcal F_{q-3}. Its compression to Z_{n-1,q-3} is the transported change in an E step from Z_{n,q}, as in Proposition 5.3. Its center terms have size A_q(m). A direct estimate of \ell_q would accumulate a scalar even in a filled state. We instead calibrate K_q+\ell_q by a filled step at the nearest lower flux divisible by three.
Put q^0=3\lfloor q/3\rfloor and r=q-q^0\in\{0,1,2\}. Start with the filled state at flux q^0-3 and increase the flux r times by F transport at the same south pole. The resulting unit vector \chi_q lies at flux q-3 and has the minimum possible hole number r. If r=0, it is the filled state itself.
Lemma 6.4 (Calibrated electron step). For q above the fixed stopping range,
For any collection of northern center terms of K_q, their expectation in \chi_q may instead be replaced by the linear reference functional of Theorem 5.6 at child flux q-3; the additional error is at most CJ_q. This remains true when the choice between the two centerings is made separately on disjoint annuli.
Proof. In the filled E step at q^0, both parent and child compressions of D(f)-C(f)\mathbf1 vanish. Proposition 5.3 therefore gives |\ell_{q^0}+\langle K_{q^0}\rangle|\le C f(q^0)(L+q^0)^{-2}. Corollary 4.6 compares this filled-step expectation first with the directly embedded lower-flux state and then with its at most two F-growth transports. Its bound is CJ_q for each comparison, proving (6.16) after adding |\ell_q-\ell_{q^0}|.
For a northern source center, the linear reference functional of Theorem 5.6, applied at child flux q-3, is the expectation in the same directly embedded filled state at q^0-3, using the common slots. The last assertion of Corollary 4.6 applies to any selected collection of source pieces and bounds the sum of absolute comparison errors by CJ_q. It therefore also permits the annulus-dependent choice of centering in the statement.
For completeness, the elementary rule for summing history bounds is as follows. At a node of flux q with positive hole number, every descendant flag is at an index at most q, and hence
on that node’s full descendant space. A node error bounded by \eta_q f(q)\mathbf1 can consequently be replaced by \eta_q S_{L,p} there. If \sum_q\eta_q\le\eta, the sum of all these node errors is at most \eta S_{L,p}: on each history, each flag appears only at ancestor fluxes, each visited at most once. This is a comparison of diagonal operators after the node form bounds have been applied. It also controls an off-diagonal remainder by its operator norm. At a node with no holes, use the exact vanishing of the centered compression instead of this rule.
Proof of Proposition 6.1 for p=1/8. Apply Proposition 5.3 recursively to D_q(f)-C_q(f)\mathbf1. The norm remainder at a node is at most C f(q)(L+q)^{-2}, and its total cost is o_L(1)S_{L,p} by (6.17) and Lemma 6.3. F transport has norm at most CB_q. Together with (6.5), its contribution is
for the flag created at that step.
At an E step with one remaining hole, q\equiv1\pmod3, so \chi_q also has one hole. Compare the child vector to \chi_q using Corollary 5.7. The difference of the K_q expectations is at most C\sup_m A_q(m). This is a two-sided form bound since it holds for every unit vector in the child space. The calibration error and all one-hole errors have total cost o_L(1)S_{L,p} by Lemmas 6.2 and 6.3.
At an E step with at least two remaining holes, Proposition 4.5 bounds the increase from K_q by C\int A_q(m)/w\,dm. Its total cost is again o_L(1)S_{L,p}. It remains to pay the positive part of \ell_q. Divide that scalar equally among the remaining flags. A fixed flag then pays at most one half of each (\ell_q)_+ at such an ancestor. The E-step intervals are disjoint, so Lemma 6.2 bounds the total payment for a flag at k by
At terminal fluxes there are only finitely many spaces. Uniformly on them, f(j)=1+O(L^{-1}), and hence
For h=0 the expression is exactly zero by rotational invariance; for h\ge1 the error is O(L^{-1})h, which is also O(L^{-1}) times the terminal flag weight. Terminal flags therefore receive the same credit 1/3-o_L(1). Combining all bounds yields
The strict margin is 5/42. Choose L=L_0 so that the total error is less than 5/84 and take c=5/84.
We record what this first estimate gives after rotation averaging. It will be applied to annular portions of the next transport interaction, with their center size factored out.
Corollary 6.5 (First averaged comparison). Let W be a neutral Hermitian interaction with bounded strength per unit area and fixed rapid locality bounds. For unit vectors \psi\in Z_{n,q} and \chi\in Z_{n',q} with hole numbers h,h',
For radius-r interactions of unit local norm one can take C_W\le C(1+r)^B for a fixed B.
Proof. To specify the rotation average on a physical zero space, let V_{n,q}(g) denote its rotation representation and define
Thus S_{L,p}^{g} acts on Z_{n,q}, whereas S_{L,p} itself acts in history coordinates. This is the history construction obtained by rotating a fixed readout frame by g; its estimates are uniform in g. Use this convention separately in each number sector.
For a local term centered at x(g)=g\cdot\mathrm{north}, use Theorem 5.6 in the frame rotated by g, with exponent a=7/4. The local term itself need not belong to a rotation-covariant family; the estimate is pointwise in g. Since (1+b)^{-a}\le C f_{L_0,1/8}(b), the local comparison is bounded by the corresponding rotated S_{L_0,1/8}. Its reference scalar cancels between the two vectors. By irreducibility of U_q, normalized rotation averaging gives the one-particle identity
where Haar measure has mass one. Proposition 6.1 for p=1/8 consequently gives
The physical area is 2\pi q, and the center density is bounded. Multiplying by that area and using \sum_{j=0}^q f_{L_0,1/8}(j)\le C(q+1)^{7/8} proves the result. The same argument applies to any center measure with bounded mass in unit balls: spread each center uniformly over a ball of fixed radius and regard its observable as centered at the new point. The resulting measure has bounded area density, and the support radius increases by only a fixed constant. Thus the preceding integral estimate applies to both discrete and continuous center measures. Finally, a rapid shell expansion multiplies the radius-r estimate by a summable series of shell norms times (1+r)^B.
6.3 The summable weight
We now fix p=3/2, keeping the already chosen L_0 and the constant in Corollary 6.5 fixed. The new scale L will be chosen at the end. Calibrate every E step with positive hole number by Lemma 6.4. Its scalar error, the branch remainders, and all F-step errors have total cost o_L(1)S_{L,3/2} by the estimates already proved. It remains to bound the centered E interactions.
Divide centers into annuli M\le1+m<2M, where M=1,2,4,\ldots. Write
On this annulus the local interaction size is at most C(q+1)^{-2}f_Ma_M. Choose a fixed sufficiently large C_0 and separate fluxes at T_M=C_0M^{1+\delta}. An annulus is present only if q+1\ge M.
Proof of Proposition 6.1 for p=3/2. First consider q\le T_M. Center the annular interaction at \chi_q. If the child has h>0 holes, the calibration state has r\le h holes, so Corollary 6.5, applied at child flux q-3, bounds the centered interaction in absolute quadratic form by
The child flag weight is at least hf(q). For M\le q+1\le T_M+1, f_M/f(q)\le C M^{p\delta}. Thus summing the relative cost (6.20) over these fluxes gives
The finitely many fluxes near the stopping range obey the same estimate after increasing its constant.
Now let q>T_M. With C_0 sufficiently large, the annulus lies in the common northern region. Center it by the linear reference functional in Theorem 5.6. Lemma 6.4 accounts for this change of centering with the already budgeted error CJ_q. For a center in the annulus, each descendant history \omega satisfies
This is also a diagonal operator inequality in the descendant history space. Indeed, for k\le M, f(k)\ge f(M); for k>M, use a=7/4>p and M/(1+k)\le C(L+M)/(L+k). The annulus has area O(M). The local readout estimate therefore bounds its centered interaction by
For rapid interactions this formula follows by applying the radius-r bound to each shell and summing its norm times (1+r)^B. The shell center stays in the same annulus even when its support extends beyond it; shells reaching the south are covered by the large-radius part of the readout estimate. Summing over q>T_M gives
Both resulting sums over dyadic M tend to zero with L. Explicitly, for every 0<\eta<2,
For M\le L this follows by summing L^{-2}M^{2-\eta}; for M>L it follows by summing M^{-\eta}. Apply this with \eta=1/16 and \eta=1/24 to (6.21) and (6.23). The node summation rule after (6.17) now gives an error o_L(1)S_{L,3/2} for the entire centered E contribution.
There is no uncompensated electron scalar in this argument. Every F flag and every terminal flag contributes -(1/3-o_L(1))f(k), while all E contributions and all remainders cost o_L(1)S_{L,3/2}. Choose a fixed L=L_1, after L_0 and the constant in Corollary 6.5, so that the combined error is at most 1/6. This proves (6.2) with c=1/6.
6.4 Rotation averaging and local interactions
The summability of f_{L_1,3/2} removes the power of the area in Corollary 6.5. We state the resulting estimate in the form needed for the energy argument.
Theorem 6.6 (Local expectations are linear in the number of holes). Let q=3(N-1) and let W be a neutral Hermitian interaction whose center density and rapid locality bounds are uniform in q. For every unit vector \psi\in Z_{n,q},
For interactions supported in radius r with local norm at most one, C_W is bounded by C(1+r)^B for a fixed exponent B. The same conclusion holds for zero-mode density matrices by linearity, with the expected value of N-\mathcal N on the right.
Proof. Use the local readout estimate with a=7/4, now comparing W_0 to S_{L_1,3/2}. Since the flux is divisible by three, the reference is the filled Laughlin expectation. The rotation average (6.19) and the second part of Proposition 6.1 give
because L_1 is fixed and \sum_{j\ge0}f_{L_1,3/2}(j)<\infty. Integration over centers costs area O(q+1), exactly as in the proof of Corollary 6.5. The result is C_Wh=3C_W(N-n); absorb the factor three into C_W. Polynomial radius costs and rapid shell summability are preserved by that argument. Decomposing a density matrix into number sectors and then into pure states proves the last assertion.
7 Local removal of interaction energy
The estimate on zero modes controls the cost of a missing electron. We now connect an arbitrary state to the zero space by a local process that removes particles. Its interaction energy decays exponentially, and its expected particle loss is bounded by its initial interaction energy. In particular, adding electrons above Laughlin filling has a uniform energy cost.
Write B_p=B(v_p), 0\le p\le 2q-2, for the normalized pair annihilators of (2.5), and put d_a=2q-1. For a rotation g\in SU(2), A(g) denotes the conjugate of an operator A by the Fock representation. Haar measure dg has mass one. The rotation average of any normalized pair row resolves the interaction:
This is Schur’s lemma on the spin-(q-1) pair space V_q.
Theorem 7.1 (Local energy descent). There are constants c>0, L<\infty, and q_0 such that, for every q\ge q_0, there is a measurable family of rapidly local physical operators J_y on \mathcal F_q satisfying
Every J_y has a definite particle loss r_y\in\{2,\ldots,L\}, so that [\mathcal N,J_y]=-r_yJ_y. The center measure has bounded mass per unit ball, and all rapid-locality bounds are independent of q and of the particle sector.
The first operation in the construction is B_0(g), which removes a pair near the point g\cdot\mathrm{north}. We then partially empty a fixed neighborhood of that point. This second operation suppresses the nearby pair correlations left behind by the first removal. We first identify the part of H_q^2 that pays for the surviving correlations.
7.1 The four-body term available for descent
The maps \mathcal L_k and W_4 are defined in (2.4) and (2.7). Thus \mathcal L_4(|u\rangle\langle v|)=B(u)^*B(v) and W_4(v\otimes w)=v\wedge w. Let P_{q,\ell} be the projection in V_q\otimes V_q onto total spin 2(q-1)-\ell, for 0\le\ell\le2q-2, and set
For large q, R_q^{\mathrm{lo}} contains precisely the small deficits \ell=0,\ldots,22. Proposition A.1, proved in the appendix, gives
for all sufficiently large q, uniformly on \mathcal F_q.
This statement contains more information than the unperturbed spectral gap. The normal-ordering identity for H_q^2 contains the full four-body term \mathcal L_4(W_4W_4^*). The finite comparison of [16, Sections 2–6] uses only the blocks \ell\le22. The appendix includes the finite certificate and its transfer to finite q, and keeps the other blocks with coefficient one. The loss construction will use precisely this part of the square.
7.2 Emptying a neighborhood without increasing distant pair energy
Choose a smooth nondecreasing T:\mathbb R\to[0,1] such that T=0 on (-\infty,1] and T=1 on [3,\infty). We choose it flat at the two endpoints and, in addition, require
For example, with \eta(x)=e^{-1/x} for x>0 and \eta(x)=0 for x\le0, one may take T(x)=\eta(x-1)/(\eta(x-1)+\eta(3-x)). The estimate follows by differentiating near x=3; an exponential e^{-1/(3-x)} times any fixed negative power of 3-x is bounded by a constant times e^{-1/(2(3-x))}. Away from that endpoint the estimate is immediate from smoothness.
For an integer M\ge2, put t_j=T(j/M) and n_j=c_j^*c_j. The two operators
define a trace-preserving channel, since K_{j,0}^*K_{j,0}+K_{j,1}^*K_{j,1}=I. Compose these channels in increasing order of j, for 0\le j<3M. Write K_\alpha for the resulting products of Kraus operators, where \alpha\in\{0,1\}^{3M}, and write \mathcal E_M for the channel. Its dual on observables is \mathcal E_M^*(O)=\sum_\alpha K_\alpha^*OK_\alpha.
The canonical anticommutation relations imply a useful exact formula. On an even normal-ordered monomial, the dual of the jth channel multiplies by t_j for each occurrence of c_j or c_j^*. Indeed, if neither occurs, the even monomial commutes with both operators of mode j and completeness gives the claim. If exactly one occurs, the loss contribution vanishes and the no-loss contribution gives t_j. If both occur, writing them as an occupation factor gives t_j^2. Consequently
Here and below terms with an orbital index outside \{0,\ldots,q\} are absent.
Lemma 7.2 (Pair energy after local loss). There is a sequence \varepsilon_M\to0 such that, for every M\ge2 and every q\ge30M,
Proof. The following two elementary estimates specialize the general pair localization bounds to the cutoff used here. In particular, the exponential estimate on distant rows will let us preserve coefficient one on their energy. Both follow directly from the coefficients in (2.5). For b\le q/2 and every fixed integer r\ge0,
For b>10M and q\ge30M,
Constants may change after decreasing c_1>0. Here is a direct verification. Set
The exact pair formula gives
When b\le q/2, these ratios, their inverses, and symmetry about b/2 show
For completeness, on the upper half i\ge(b-1)/2, the first factor in the ratio is at most one and the second is at most \exp\{-(2i+1-b)/(b+1)\}. Summing logarithms from a middle index gives the Gaussian upper bound relative to the middle value. In the range |i-b/2|\le\sqrt b, the absolute value of that logarithm is at most C(1+|i-b/2|)/b. Summing these lower bounds and using \sum_i p_{q,b}(i)=1 bounds the middle value by C/\sqrt b. Insertion in (7.11), followed by summing Gaussian moments, proves (7.9).
To prove (7.10), there is nothing to check if b>q+3M, because the sum is empty. Otherwise b\le q+3M\le11q/10, so 2(2q-1)/[b(2q-b)]\le C/b in (7.11). For every allowed i\le2b/5 and b\ge20, the ratio in (7.11) is at least 4/3. Starting with i<3M<3b/10 and taking at least b/10-O(1) steps toward 2b/5 gives p_{q,b}(i)\le Ce^{-c b}, since each probability is at most one. The square root of (7.11) is therefore at most C\sqrt b\,e^{-c_1b}, and there are at most b terms. This proves (7.10).
The modified row vanishes when b\le M. For M<b\le10M, put x=b/(2M) and t=T(x). The smooth even function z\mapsto T(x+z)T(x-z) has zero first derivative at zero. By (7.5), every derivative of positive order there is bounded by C_r\sqrt{1-t}. Taylor expansion through degree 41, with a bounded remainder of order 42, and (7.9) yield
We used \|c_jc_i\|\le1. More explicitly, the degree-r contribution is bounded by
and the remainder is at most CM^{-42}b^{21+1/4}.
Let \delta=M^{-8} and s=1-t+\delta. For any vector \phi, Cauchy’s inequality gives
Since t^4+s\le1+\delta, (7.12) bounds the second term by CM^{-3/2}\|\phi\|^2. Summing over the O(M) central rows costs CM^{-1/2}\|\phi\|^2. The additional coefficient \delta also disappears in this error: (7.9) with r=0 implies \sum_{M<b\le10M}\|B_{b-1}\|^2\le CM^{3/2}.
Finally, for b>10M the coefficients of \widetilde B_{b-1}-B_{b-1} are supported where i<3M or j<3M. The increasing ordering reduces this to i<3M. Equation (7.10) bounds this difference in operator norm by Cb^{3/2}e^{-c_1b}, while normalization of the pair vector gives \|B_{b-1}\|\le\sqrt b. The norm of the difference of the two row squares is therefore summable over b>10M, with sum at most Ce^{-c_3M}. Combining the three ranges proves the assertion, with \varepsilon_M\le C(M^{-1/2}+M^{-13/2}+e^{-c_3M}).
7.3 Rotation averaging suppresses the small-deficit blocks
Retaining only the rows whose index sum exceeds M gives a positive operator on the two pair factors:
If the sum includes all k, the operator equals I by Schur’s lemma. Consequently 0\le A_{q,M}\le I. This bound handles every retained block with the same coefficient one as in (7.4). It remains to make the coefficients on the finitely many unretained blocks small and bound their lifts by H_q.
Lemma 7.3 (Vanishing weight on fixed deficits). For A_{q,M} in (7.13), there are coefficients 0\le a_{q,M,\ell}\le1 such that
For every fixed \ell\ge0,
Moreover, for each fixed \ell there is C_\ell<\infty such that
for all sufficiently large q.
Proof. The tensor product of two spin-(q-1) representations is multiplicity free. Hence rotation invariance and 0\le A_{q,M}\le I prove the first assertion. Put a=q-1 and d_{q,\ell}=4q-3-2\ell. If C_{q}(\ell,k) is the coupling coefficient of v_0\otimes v_k in total spin 2a-\ell at total lowering degree k, then
The unrestricted sum, including all k, has coefficient exactly one.
We give the fixed-k limit, including its normalization. At a fixed total degree, the two spin lowering operators, divided by \sqrt{2a}, converge to multiplication by two independent oscillator variables X,Y. The highest vector of deficit \ell converges to (X-Y)^\ell/\sqrt{2^\ell\ell!}: applying the raising operator gives successive coefficient ratio -\sqrt{(\ell-p)/(p+1)} in the limit, which fixes this normalized vector. Normalized subsequent lowering multiplies by (X+Y)/\sqrt{2(k-\ell)} at degree k. Thus the degree-k coupled vector converges, in the orthonormal monomial basis, to
Its coefficient of Y^k/\sqrt{k!} has squared modulus 2^{-k}\binom{k}{\ell}, and hence
There are only finitely many degrees below a fixed M. Subtracting these from the exact unrestricted coefficient one gives
The identity \sum_{k=\ell}^{\infty}2^{-k}\binom{k}{\ell}=2 proves (7.14). This finite-head argument requires no uniform convergence over an unbounded set of coupling coefficients.
For (7.15), choose a normalized highest vector z_{q,\ell}=\sum_{p=0}^{\ell}s_pv_p\otimes v_{\ell-p}, with \sum_p|s_p|^2=1. Its wedge annihilator is \sum_p\overline{s_p}B_{\ell-p}B_p. Every B_{\ell-p} uses only the first \ell+2 orbitals and has norm at most \sqrt{\ell+2}. Therefore
Resolve P_{q,\ell} by the orbit of its highest vector and use (7.1). This yields
whose coefficient is bounded for fixed \ell.
Proof of Theorem 7.1. For the moment fix M, and define
with counting measure in \alpha. Completeness of the loss channel and (7.1) give \int J_y^*J_y\,d\nu_q=H_q. Lemma 7.2, applied to B_0(g)\psi and then averaged, gives
The equality between the averaged pair products and the lifted four-body operator uses ordered tensor factors. There is no factor of two: B(v\wedge w)=B(w)B(v) and the lift sums each ordered pair once.
By Lemma 7.3 and positivity of the lift,
Fix c_0=1/50 in (7.4). Choose M large enough, and then q large enough, that \varepsilon_M+\sum_{\ell=0}^{22}C_\ell a_{q,M,\ell}\le c_0/2. Equations (7.4) and (7.17) prove (7.2) with c=c_0/2.
Each K_\alpha is a product of 3M operators of particle loss zero or one, so J_{g,\alpha} has loss between 2 and L=3M+2. All modes involved in J_{g,\alpha} have index below 3M, apart from identity factors. To see operator-norm locality directly, use the frame isometry \mathsf S_q:U_q\to\ell^2(\Lambda_q) and write c(f)=B(f) on the slot Fock space. If P_R cuts off slots outside the radius-R ball around g\cdot\mathrm{north}, the canonical anticommutation relations give
The last estimate follows from Lemma 3.1 and the slot volume bound, with a larger decay order before summing squares. The same estimate for a product follows by telescoping its finitely many factors, or by Lemma 3.4. Thus the jumps are rapidly local around g\cdot\mathrm{north}, uniformly in q. There are only 2^{3M} auxiliary labels, with M now fixed. The pushforward of (2q-1)dg to the physical sphere has area density (2q-1)/(2\pi q); the remaining rotation angle has mass one. Including all auxiliary labels therefore gives total center density 2^{3M}(2q-1)/(2\pi q), uniformly bounded in q for this fixed M. These observations prove all locality and density assertions.
7.4 Particle loss, excess charge, and a coercive Fock Hamiltonian
Let q=3(N-1) and let \rho_t evolve by the trace-preserving equation whose dual generator is
This is a finite-dimensional Lindblad generator [10]. Positivity and trace preservation also follow directly by iterating variation of constants, with the completely positive gain map \rho\mapsto\int J_y\rho J_y^*\,d\nu_q(y) and the no-jump map \rho\mapsto e^{-tH_q/2}\rho e^{-tH_q/2}. We write \langle O\rangle_t=\operatorname{Tr}(\rho_tO).
Proposition 7.4 (Control of particle number). There are constants C_{\mathrm{num}}<\infty, \mu>0, a>0, and C_G<\infty, independent of sufficiently large q=3(N-1), such that
The operator
satisfies
for a constant g>0, with P_{\mathrm L,N} extended by zero on the other Fock sectors. For every initial density matrix, the evolution (7.18) obeys
Every limit point \rho_\infty is supported on \ker H_q, and
Proof. Theorem 7.1 gives \mathcal D_q(H_q)\le-cH_q, proving (7.22). Since [\mathcal N,J_y]=-r_yJ_y,
Integration proves (7.23) with C_{\mathrm{num}}=L/c. Compactness of the density matrices in each fixed finite-dimensional Fock space gives limit points as t\to\infty. By energy decay each is supported on \ker H_q. Lemma 2.1 shows that this kernel contains no sector of particle number exceeding N. Applying (7.23) to a state of definite particle number n and passing to a limit point gives n-N\le C_{\mathrm{num}}\langle H_q\rangle_0. This proves (7.19) on each sector, and hence on Fock space.
Choose 0<\mu\le\min(1,(2C_{\mathrm{num}})^{-1}). In sectors n\le N, G_q=H_q+\mu(N-n) dominates \mu(H_q+N-n). In sectors n>N, (7.19) gives G_q\ge H_q/2 and H_q+n-N\le(1+C_{\mathrm{num}})H_q. This proves the first inequality in (7.21) with a=\min(\mu,[2(1+C_{\mathrm{num}})]^{-1}). For n\ne N, |N-n|\ge1; for n=N, the uniform gap and uniqueness in Theorem 2.2 give H_{N,q}\ge(1/25)(I-P_{\mathrm L,N}). Thus the second inequality holds with g=a/25.
Finally, energy decay and number control give
Take C_G=1+\mu C_{\mathrm{num}}/a. Passing to a limit point, where H_q=0, proves (7.25).
8 Relative bounds and stability
The preceding sections provide two estimates with different roles. The zero-mode bound controls a local observable after particles have been removed. The loss evolution connects an arbitrary state to that zero space at a cost measured by its initial interaction energy. We first combine them into a relative form bound. Spectral transport will then put the disorder perturbation in the class covered by that bound.
Throughout this section, q=3(N-1) is sufficiently large, \Omega\in Z_{N,q} is the unit Laughlin vector, and H=H_q. Choose the fixed \mu>0 from Proposition 7.4 and write
Thus G is positive, has kernel \mathbb C\Omega, and has a uniform gap. Moreover it controls both H and |N-\mathcal N|.
8.1 A relative bound for terms that annihilate the ground state
We use the local norm \|A\|_{x,\ell} of (3.10) at one fixed order \ell. Partition the sphere into cells of uniformly bounded diameter whose centers satisfy the two-dimensional volume bound of Section 3. For a continuous interaction, collect all terms centered in a cell and assign their integral to that cell’s center. Moving a center a bounded distance changes the local norm by a fixed factor. We normalize the total localization norm in each cell to at most one.
Physical operators act trivially on the complementary slot modes; the inequalities below are on physical Fock space. Averaging ball approximants over total-slot-number rotations preserves support and approximation error, so approximants of a neutral operator may be chosen neutral. Taking Hermitian parts gives Hermitian approximants.
Choose \ell larger than the polynomial support-radius exponent in Theorem 6.6, and larger than any fixed geometric exponents needed below. A dyadic decomposition into ball approximants shows that the zero-mode estimate extends to interactions with bounded total \|\cdot\|_{x,\ell} per cell. Explicitly, the shell of radius 2^k has norm O(2^{-k\ell}), while its zero-mode cost is O(2^{kB}) for a fixed B<\ell; the series converges.
Proposition 8.1 (Relative form bound). For this fixed sufficiently large \ell, there is a constant C independent of q such that
whenever the A_x are physical, neutral, Hermitian operators satisfying A_x\Omega=0 and \|A_x\|_{x,\ell}\le1. If the sum or integral of localization norms in each cell is at most S, the conclusion becomes -CSG\le\sum_xA_x\le CSG.
Proof. Fix q for the moment and let K=K_q be the least constant in (8.2) for the stated class. It is finite: every admissible sum annihilates \Omega on both sides, its norm is bounded by the finite number of cells, and G has a positive gap on \Omega^\perp. This observation gives no useful uniform bound; we obtain one from the loss evolution.
Let J_y be the jumps of Theorem 7.1, including their bounded auxiliary indices in the measure dy. They obey
The second assertion follows by taking the expectation of the first in \Omega. Put C_{xy}=[A_x,J_y] and D_{xy}=1+d(x,y). Since A_x is even, the ordinary commutator vanishes for disjointly supported approximants, including when J_y is odd. Lemma 3.4(iii) gives
The last estimate retains the same order \ell required of A_x. Thus, after integration in y, the positive operators C_{xy}^*C_{xy} remain in the class whose best relative-bound constant is K. Fixing one polynomial norm makes this closure possible.
Every C_{xy} annihilates \Omega, because both A_x and J_y do. Therefore C_{xy}^*C_{xy} is a physical, positive, neutral, centered operator to which the definition of K applies. Choose
The two-dimensional volume bound and (8.3) give
Indeed for each fixed x the integrated operator has localization norm at most C\int D_{xy}^{b-\ell}\,dy\le C, and kills \Omega. Collect it as a single admissible term at cell x. This also explains the continuous-family extension in the statement.
Let \rho_t be the state evolution dual to the loss generator, starting at an arbitrary density matrix \rho_0. All observables in the desired inequality preserve number, so replacing \rho_0 by its number-diagonal part changes none of the relevant expectations. For A=\sum_xA_x, the Lindblad identity reads
Apply Cauchy–Schwarz to this sum with weights D_{xy}^{-b} and D_{xy}^{b}. Since \sum_xD_{xy}^{-b}\le C uniformly in y, (8.5) yields
The energy-descent estimates give constants c,C>0 such that
Integrating (8.6) therefore costs at most C\sqrt K\operatorname{Tr}(\rho_0 G).
Along a sequence t_j\to\infty, finite dimensionality gives a limit state \rho_\infty supported on Z_q. Its sectors have n\le N by Lemma 2.1. The zero-mode bound and \langle\Omega,A\Omega\rangle=0 show that
Combining the two bounds, and then taking the supremum over all admissible interactions and states, gives
Solving this quadratic inequality for \sqrt K proves a bound independent of q, as required.
8.2 Transporting the ground state
The perturbation is not termwise centered in the sense of Proposition 8.1. Spectral transport produces that property. We give the argument explicitly because it must follow the perturbed ground line rather than keep the original line fixed. The smooth frequency filter implements the quasiadiabatic idea of [6] in the exact spectral-flow form of [2]; the locality estimates needed here were established in Section 3.
Let \varphi be real and measurable, \|\varphi\|_\infty\le1. On Fock space set
The coherent resolution (2.3) writes V as a bounded-density integral of neutral Hermitian terms
They are rapidly local with uniform bounds by Lemma 3.1. The same holds for H, using the rotations of v_0=e_0\wedge e_1:
The measure has uniformly bounded density on the physical sphere. In particular every H_s has uniform interaction bounds for |s|\le1, even though \|V\| can grow with N.
Fix g_0=1/25 and work initially on a connected parameter interval containing zero where the N-sector ground state is simple and the gap above it exceeds g_0/2. Such an interval exists at every fixed flux by finite-dimensional perturbation theory. Choose once and for all a smooth odd real function F satisfying
It can be chosen with an inverse Fourier kernel having every absolute polynomial moment. The 1/\omega tail is square-integrable and has integrable derivatives of all positive orders; near time zero Plancherel gives local integrability, and repeated integration by parts gives arbitrary decay for large time.
For each term of V, define Y_x(s) by applying this frequency filter with respect to H_s. In an eigenbasis of H_s,
Oddness of F makes Y_x anti-Hermitian. Every Y_x is physical, neutral, and rapidly local with uniform bounds; put Y(s)=\int Y_x(s)\,dA(x) and solve
This unitary preserves number. If P_s is the N-sector ground projection, the usual spectral derivative formula and (8.7) give P_s'=[Y(s),P_s]. Consequently U(s)P_0U(s)^*=P_s. Neutrality is important here: the matrix elements crossing the ground projection stay in the N-particle sector. No assertion about a perturbed Fock-space gap is needed.
For each x separately, define
These are Hermitian neutral physical operators. For an excited N-sector eigenvector a and the ground vector 0, their unconjugated off-diagonal matrix element is
Hermiticity gives the reverse vanishing. Thus each Q_x(s) preserves \mathbb C\Omega, and A_x(s)\Omega=0 exactly. The commutator with H_s and the finite-parameter conjugation by U(s) preserve rapid locality, uniformly on the bootstrap interval. The scalar satisfies |a_x(s)|\le\|Q_x(s)\|; it can be assigned to the same center. Hence the interaction A_x(s) satisfies Proposition 8.1 with a uniform size bound.
Let E_0(s) be the N-sector ground energy. Differentiating the pulled-back Hamiltonian and taking its expectation in \Omega gives
All differentiation is finite-dimensional; the integral notation may equally be collected into cells. On the N-sector, G=H. Integrating in either parameter direction yields
The kernel on this interval is \mathbb C\Omega, so the min–max principle gives a gap of at least (1-C|s|)g_0.
Choose \lambda_*>0 with \lambda_*\le1 and C\lambda_*\le1/4. The improved lower bound 3g_0/4 prevents the gap from reaching the bootstrap boundary g_0/2 anywhere in [-\lambda_*,\lambda_*]. Indeed a first boundary point would contradict continuity of the ordered eigenvalues and (8.11). The construction therefore extends over this entire interval at every sufficiently large flux. Taking \Delta_*=g_0/2 proves Theorem 1.1.
A Retaining the unused four-body blocks
The local loss construction requires a stronger operator inequality than the unperturbed gap: most of the normal-ordered four-body term must remain on the right-hand side. We give the full finite-dimensional calculation that establishes this strengthening. The seven auxiliary squares, their rational certificate, and the finite-flux transfer are adapted from [16, Sections 2–6 and 8]. The proof below retains the four-body blocks that are discarded when only the gap is sought.
We use the lift and wedge maps of (2.4) and (2.7), with increasing orthonormal wedges of norm one. Thus B(v\wedge w)=B(w)B(v), and the domain of W_4 uses ordered pair factors. Write a=q-1 and H=H_q; the conventions give
The dagger in this appendix denotes the same adjoint as the star in the main text.
The tensor product V_q\otimes V_q contains one copy of each spin 2q-2-l, 0\le l\le 2q-2. Let P_{q,l} be its orthogonal spin projection and define
The spin-block label used in the calculation below is D=l+1; thus R_q^{\mathrm{lo}} consists exactly of 1\le D\le23.
Proposition A.1 (Retained four-body blocks). For every fixed 0<c_0<1/25 there exists q_0 such that, for every integer q\ge q_0, the following inequality holds on the entire Fock space \mathcal F_q:
The threshold is independent of particle number.
We prove the proposition by comparing a positive rotational average of seven explicit squares with the normal-ordered terms of H_q^2. The comparison uses the target four-body blocks 1\le D\le23 only. All other target blocks consequently remain with coefficient one.
Lemma A.2 (Normal-ordered square). On \mathcal F_q,
Proof. In normal ordering B_p^\dagger(B_pB_r^\dagger)B_r, only the two inner annihilators cross the two inner creators. Two, one, or zero contractions leave two-, three-, or four-body terms, respectively. On two particles, H=\Pi_{V_q} is a projection, so the two-body coefficient is \Pi_{V_q}. The term with no contractions is
There is no extra factor of two: this sum, and the defining basis of V_q\otimes V_q, both use ordered pairs. On three particles, H=W_3W_3^\dagger, since W_3 restricted to v_p\otimes U_q is the map B_p^\dagger from one to three particles. Subtracting its two-body contribution from H^2 therefore determines the remaining coefficient as
Normal-ordered coefficients are determined successively by these restrictions, proving the identity on Fock space.
A.1 Spin coefficients and their limits
The three-body comparison will use the exact spin spectrum of the wedge map. The four-body comparison will use only finitely many coupling coefficients and their limits.
For this auxiliary calculation we simultaneously change the signs of all pair rows from (2.5), so that v_0=-e_0\wedge e_1, and use the normalized lowering bases e_p and v_p. This common phase change leaves H_q and the intrinsic wedge maps and spin projections unchanged. For spin j, lowering from label p to p+1 has coefficient \sqrt{(p+1)(2j-p)}. Write (s)_p=s(s-1)\cdots(s-p+1), with (s)_0=1.
Lemma A.3 (Pair coefficients). The coefficient of e_i\wedge e_j in v_p, for i<j, vanishes unless i+j=p+1, and otherwise equals
For fixed p,i,j, its limit is
Proof. Apply simultaneous lowering p times to -e_0\wedge e_1 and divide by \sqrt{(2q-2)_p p!}. Expand the lowering operator binomially. Combining the two contributions to each increasing pair gives (A.6). Taking the limit gives (A.7). The normalization can also be checked directly: the square of the coefficient in (A.6) is
and differentiating (1+x)^q gives
Take the coefficient of x^{p+1} and halve the sum to restrict to i<j.
The elementary tensor product rule decomposes spins j_1,j_2 into one copy of each spin j_1+j_2-z, for 0\le z\le\min(2j_1,2j_2). Let R_{3,z} be the corresponding projection in V_q\otimes U_q, and put
For q\ge2, the allowed indices are 0\le z\le q.
Lemma A.4 (Three-body Gram eigenvalues).
In particular W_3R_{3,z}=0 for z=0,1,3 whenever these indices are allowed. For fixed z,
Proof. Identify V_q\otimes U_q with tensors antisymmetric in their first two positions. Then W_3 is \sqrt3 times full antisymmetrization. Its Gram operator is the compression of I-P_{13}-P_{23}, where P_{ij} swaps tensor positions. The two swap compressions coincide, since conjugation by P_{12} interchanges them and P_{12}=-I on the domain. By equivariance and multiplicity-freeness they act by the same scalar b_z on each spin block.
A highest vector of that block has coefficients s_p on v_p\otimes e_{z-p}, 0\le p\le z, satisfying
This follows by applying the raising operator. Using (A.6), the coefficient of the compressed P_{23} image on v_0\otimes e_z is
with the first term absent for z=0. Here the ordered tensor coefficients of a normalized wedge include a factor 1/\sqrt2. Iteration of (A.10) gives
Substitution gives q_z=-2b_z in the form (A.8). The three stated null sectors have q_z=-1, and (A.9) follows directly.
We will repeatedly use a fixed-deficit limit of this same calculation. In a product of spins j_1,j_2, total lowering deficit means T=j_1+j_2-m, where m is the total magnetic quantum number. Coefficients below are with respect to normalized monomials X^pY^{T-p}/\sqrt{p!(T-p)!}, and are zero outside the stated index ranges.
Lemma A.5 (Fixed-deficit coupling limit). Suppose j_1,j_2\to\infty and j_2/(j_1+j_2)\to u^2, where 0<u<1. Put v=\sqrt{1-u^2}. For fixed integers 0\le z\le T, the normalized coupled vector of spin j_1+j_2-z at total lowering deficit T can be chosen with real coefficients converging to the coefficients s^{(u)}_{z,T,p} of
Descendants in every copy are obtained by normalized lowering, so the matching of bases between equal-spin copies is intertwining.
Proof. At T=z, the raising equation gives the adjacent ratio
With sign (-1)^z at p=0, normalization yields the coefficients of (uX-vY)^z/\sqrt{z!} in the limit. The change of variables (X,Y)\mapsto(uX-vY,vX+uY) is orthogonal, so these polynomials have norm one in the normalized-monomial inner product. Normalized lowering from T to T+1 divides the sum of the two lowering operators by
In the limit this acts by multiplication by (vX+uY)/\sqrt{T-z+1}. Induction proves the statement for fixed descendants.
A.2 Rotational averages of explicit squares
We construct a positive rotational average and compare its three- and four-body terms with those of H_q^2. This section specifies the finite inequalities needed; Subsection A.5 proves them by exact rational arithmetic.
Haar measure dg on SU(2) is normalized to have total mass one. For an operator A, write A(g)=U(g)AU(g)^\dagger, with the appropriate Fock representation. Schur averaging sends a rank-one operator on an irreducible spin-j space to its trace times I/(2j+1). For several equivalent copies, it acts in the same way on the spin factor and retains the matrix between copies.
For each of the seven rows in Subsection A.5, the integer t_\rho lies in \{0,\ldots,7\}. Set
The row specifies real coefficients \lambda_\rho and \alpha^\rho_{pj} for (p,j)\in\mathcal S_\rho; unlisted entries are zero. Every coefficient sum for row \rho below is over \mathcal S_\rho. Our comparison operator is
Thus only modes 0,\ldots,8 occur in these auxiliary squares.
For a single row, omit \rho and put i=p+j-t, k=p'+l-t. Define
Reordering c_ic_k^\dagger=\delta_{ik}-c_k^\dagger c_i gives the two-, three-, and four-body terms of F^\dagger F:
Let A_2,A_3,A_4 denote these terms, summed over rows and averaged with factor d_a. Thus
A.2.1 The three-body comparison
Before wedging, (A.14) is a matrix on V_q\otimes U_q. Its nonzero entries preserve T=p+j, and T\le15. Averaging therefore gives
for all sufficiently large q, where e_z^q is the trace of the unaveraged matrix in that spin block. By Lemma A.5, with u=1/\sqrt3, these traces converge to
where s=s^{(1/\sqrt3)} and empty inner sums are zero. The condition i=k in (A.14) is exactly the equality of the two values of T.
The exact calculation in Subsection A.5 proves
There are finitely many strict inequalities, d_{3,z}/d_a\to3/2, and the omitted blocks z=0,1,3 are annihilated by W_3. Consequently, for all sufficiently large q,
A.2.2 The four-body comparison before taking limits
Let
be the wedge map. The second tensor factor decomposes into spins q-r, with r odd, 1\le r\le q. In its lowering bases use the sign of Lemma A.5; at r=1 this is precisely the basis v_p.
A copy of spin 2q-1-D is obtained by coupling a=q-1 with q-r at deficit D-r. Denote its vector at total deficit T by \rbket{D,T;r}_q. Its physical orbital-index sum is 1+T, and it is a highest vector when T=D. For fixed D,T and sufficiently large q, the allowed copy labels are
Define the real finite-flux coefficients by
and extend them antisymmetrically in j,k. By two applications of Lemma A.5, they converge to
interpreted as zero if r>j+k. The formula holds for either ordering of j,k, by antisymmetry. It follows by applying Lemma A.5 first to the two single-particle spins and then to the two pair spins.
After averaging (A.15), its spin-2q-1-D block before wedging is a copy matrix E_D^q times the spin identity, multiplied by d_a/d_D, where
Only 1\le D\le23 contribute: every unaveraged term has
For these finitely many D, entrywise convergence gives E_D^q\to E_D, with
where i=p+j-t_\rho, k=p'+l-t_\rho, and T=p+j+k. The exact finite-flux matrix E_D^q is given by the same formula with each S_r replaced by S_r^q.
The target term \mathcal L_4(W_4W_4^\dagger) is obtained from the r=1 summand, since that summand is V_q\otimes V_q. Thus its copy matrix, in the units just used, is (d_D/d_a)\chi, where
The summands of the target with 1\le D\le23 equal \mathcal L_4(W_4R_q^{\mathrm{lo}}W_4^\dagger). Since A_4 has no other spin blocks, the comparison with A_4 uses only this part of the target. We keep \mathcal L_4(W_4R_q^{\mathrm{hi}}W_4^\dagger) separately.
Set
The star is a limit label, not an adjoint. The exact certificate is
We next show how these finite inequalities give the stated bound uniformly in particle number. Subsection A.5 supplies their integer data and exact rational verification.
A.3 A relative error bound for finite spheres
The limiting Gram matrices have kernels, so their positivity cannot be transferred by assuming that their ranges vary continuously. Instead, we compare the annihilators themselves. An exact diagonal change of variables reduces every error to a fixed finite family of pair-generated annihilators. This gives an error relative to H_q, uniformly on the full Fock space.
For the local argument, let \mathcal F_{\mathrm{loc}} be the exterior algebra on the 25 orthonormal modes e_0,\ldots,e_{24}. For q\ge24 we identify it with the Fock space of the first 25 orbital modes in U_q. By (A.7), each limiting pair vector v_p^* with p\le23 lies in \bigwedge^2\mathbb C^{25}. Contraction by these vectors is defined on \mathcal F_{\mathrm{loc}} by the same exterior-algebra convention as before.
Lemma A.6 (Compression and annihilator bounds). Let W be a linear map between finite-dimensional Hilbert spaces, G=W^\dagger W, and let C be self-adjoint on the domain of W. Then
On \mathcal F_{\mathrm{loc}}, for any fixed finite collection A_b=c_kc_jB(v_p^*) with 0\le p\le23 and 0\le j,k\le24,
where C_0 depends only on the collection.
Proof. The two positivity statements both assert that the quadratic form of C is nonnegative on \operatorname{ran} G=\operatorname{ran} W^\dagger. For the second assertion, use \rbnorm{c_kc_jB(v_p^*)\psi}\le\rbnorm{B(v_p^*)\psi} and sum; one may take C_0 to be the largest multiplicity of a pair label p.
Lemma A.7 (Uniform transfer). For q\ge24 and 1\le D\le23, put
Assuming (A.25), there is a scalar \rho_q\ge0, independent of D and tending to zero as q\to\infty, such that
on the entire Fock space \mathcal F_q.
Proof. An exact change of variables. Take q\ge24. All annihilators in (A.27), including those in h_q, involve only the modes 0,\ldots,24. First work on \mathcal F_{\mathrm{loc}}. Define the positive diagonal operator
on each basis wedge \rbket A. This local Fock space is fixed as q varies. Thus \Delta_q and \Delta_q^{-1} converge in norm to I; also 0<\Delta_q\le I.
The pair coefficient formula (A.6) gives
Checking the factors attached to the removed orbital labels on a basis wedge gives the exact identities
These are identities on the local Fock space, with the inverse diagonal acting on the output particle sector. Repeated removed labels make both sides zero. In particular, solving (A.28) for B(v_p^*)\Delta_q and using r_p(q)\ge1 and \rbnorm{\Delta_q}\le1 gives
The error is controlled by pair energy. Fix D. Index a finite family by b=(p,j,k) with p+j+k=D and j<k, and put
Equations (A.23) and (A.29) yield
The coefficients are real, and Lemma A.5 gives \beta_{rb}^q\to\beta_{rb}^*:=S_r(D,D;p,j,k). Hence the finite real symmetric matrices
The quadratic expression in (A.27) is consequently
Its limiting expression before the outer diagonals is
Indeed, the certificate (A.25) and Lemma A.6, applied to the map with columns w_{Dr}^*, give positivity before lifting; the lift \mathcal L_4 preserves positivity.
For clarity, the perturbation estimate does not require M_*\ge0. Let R_q be the block matrix with entries
Its norm tends to zero, since both its index set and the local Fock space are fixed. For every vector \phi,
Combine this estimate with (A.31), take \phi=\Delta_q\psi, and apply (A.30). This proves (A.27) on the local Fock space with a coefficient tending to zero. Taking a maximum over the fixed set 1\le D\le23 gives a common \rho_q.
Additional particles are spectators. Order the 25 local modes before all other modes in the Fock factorization. Every operator in (A.27) acts on the local factor alone. Tensoring the local inequality with the identity proves it on \mathcal F_q, with the same \rho_q, regardless of the number of occupied modes outside this factor.
The allowance \varepsilon I in the certificate must also be paid for in pair energy. Here it is useful to sum over the orthonormal highest vectors before estimating their wedges. Bessel’s inequality then avoids an extra factor equal to the number of spin copies.
Proposition A.8 (Four-body estimate). For the coefficients in Subsection A.5,
uniformly on \mathcal F_q.
Proof. Haar averaging the matrix unit \rbket{D,D;r}_q\rbbra{D,D;s}_q gives the corresponding copy matrix unit tensored with the spin identity, divided by d_D. Therefore, on the blocks 1\le D\le23, the low-block target minus A_4, with the \varepsilon I allowance added, is
Lemma A.7, conjugated by each rotation, bounds this below by -o(1)H, because Schur averaging gives
The number of blocks in the comparison is fixed, so this error remains uniform in particle number.
To bound the allowance, fix D and write
The uncoupled vectors on the right are orthonormal. So are the highest vectors on the left: distinct r belong to orthogonal spin summands of the second pair factor. Thus S^q(S^q)^T=I. Apply the contraction S^q\otimes I to the Hilbert-space-valued vector (c_kc_jB_p\psi)_b. It follows that
This uses orthogonality before wedging; the vectors w_{Dr}^q themselves need not be orthogonal. The number of triples on the right is
Conjugate by rotations and integrate. Each pair norm contributes \rbip\psi{H\psi}/d_a, so the total allowance is bounded by
Removing the allowance proves (A.32). No block of R_q^{\mathrm{hi}} has entered this estimate.
A.4 The three-body tail and the retained-block inequality
The preceding comparison has used only the low four-body target. It remains to control the three-body blocks above z=15 by pair energy and combine the estimates.
Lemma A.9 (Three-body tail). For sufficiently large q,
where
Proof. For 16\le z\le q, the bracket in (A.8) is positive, since it is at least 2z-2. Thus only odd z contribute negatively. A normalized highest vector of R_{3,z} is \sum_{p=0}^zs_pv_p\otimes e_{z-p}. Its orbit resolves that spin projector with factor d_{3,z}. After wedging and lifting, its quadratic form is
Averaging each summand proves (A.33) with (A.34).
For q\ge4, the ratios in (q)_z/(2q-2)_z are nonincreasing, so
The summands, extended by zero for z>q, are therefore dominated by 6z(z+1)(2/3)^z. Dominated convergence and (A.9) give
The last identity follows by writing z=17+2m and using the geometric-series identities for \sum t^m, \sum mt^m, and \sum m^2t^m at t=1/4.
Proof of Proposition A.1. Write T_{\mathrm{lo}}=\mathcal L_4(W_4R_q^{\mathrm{lo}}W_4^\dagger) and T_{\mathrm{hi}}=\mathcal L_4(W_4R_q^{\mathrm{hi}}W_4^\dagger). The normal-square identity, the three-body comparison (A.20), and the tail estimate give
By (A.32), T_{\mathrm{lo}}\ge A_4-(1222\varepsilon+o(1))H. Using \mathcal K_q=\eta H+A_3+A_4\ge0 from (A.16), we obtain
The coefficient of H tends to
For fixed 0<c_0<1/25, choose q large enough that this coefficient exceeds c_0 and discard the positive operator \mathcal K_q. This is (A.4). The matrix comparisons involved finitely many fixed orbital modes, the transfer estimates held on full Fock space, and the tail estimate was uniform in particle number. Therefore the same threshold applies simultaneously to every sector.
A.5 The finite rational certificate
We finish by verifying the two finite inequalities (A.19) and (A.25) used above. The seven integer rows and all rational formulas are given here. Starting from the integer rows in Subsection A.5.1, evaluate the rational three-body traces in Subsection A.5.2 and the rational four-body matrices in Subsection A.5.3. The margin and coefficient-sign tables in those sections record the resulting checks. The formulas below determine every value using only integers and rational numbers.
A.5.1 Row data
Let P=10^7. The first two numbers of each row are t and \ell=P\lambda. An entry pj:a specifies the integer a_{pj}, with p and j parsed as separate single-digit labels; omitted entries are zero. Continuation lines belong to the preceding row. Define
Every nonzero entry has 0\le p+j-t\le8.
In particular P^2\eta=\sum_\rho\ell_\rho^2=93527408868499.
A.5.2 Three-body arithmetic
For c\in\{1,2\}, an integer T\ge0, and integers z,p, define
and set it to zero if z or p lies outside [0,T]. Expanding (A.11) gives
Substitution in (A.18) and (A.36) cancels all radicals:
where
with value zero on empty levels. For each z\in\{2,4,5,\ldots,15\}, evaluate (A.38) and form the exact rational margin m_z=\frac32(3z-1)(-1/2)^z-e_z. Write 10^6m_z=n_z/d_z with integers n_z,d_z and d_z>0. Integer division gives the floors \lfloor n_z/d_z\rfloor listed below:
| z | 2 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| floor | 1298313 | 211317 | 249 | 250 | 249 | 250 | 250 | 250 | 249 | 250 | 250 | 6470 | 250 |
All are positive, proving (A.19).
A.5.3 Four-body arithmetic
Fix 1\le D\le23; all copy indices below lie in \mathcal R_D. Put
The matrices Y,Z are rational. Define
with value zero for r>j+k. Two applications of (A.11) give
Therefore
where i=p+j-t_\rho, k=p'+l-t_\rho, and T=p+j+k. Both entry sums are ordered. To verify the cancellation, multiply the two factors in (A.39) by the two factors (A.36); their remaining square root is exactly the factorial and power-of-two factor displayed in (A.40).
For an increasing quadruple A of nonnegative indices with sum D+1, put f(A)=\prod_{b\in A}b!. If (x,y,j,k) lists its elements, let \sigma(x,y,j,k) be the sign of sorting this list into increasing order. In each summand below put p=x+y-1, and define
Combining (A.7) and (A.39), the coefficient of w_{Dr}^* on the Slater wedge A is \sqrt{u_r/f(A)}L_r(A). Thus
All exponents of two in these formulas are integers, since r,s are odd.
Let D_u=\operatorname{diag}(u_r) and D_{\sqrt u}=\operatorname{diag}(\sqrt{u_r}). The matrix in (A.25) equals D_{\sqrt u}MD_{\sqrt u}, where
Thus it suffices to check M\ge0 using rational arithmetic.
To check positivity for each D=1,\ldots,23, form Y and Z from (A.40) and (A.42), then form B and M from (A.43), using \varepsilon=3/10^6. All sums range over the printed rows and the finite index sets specified above. Compute with exact fractions throughout. If d=|\mathcal R_D|, initialize J=I_d. For b=1,\ldots,d, compute in order
Then \det(xI+M)=x^d+c_1x^{d-1}+\cdots+c_d. For example, this recurrence follows by multiplying the polynomial adjugate of xI+M by xI+M and comparing coefficients, together with the derivative-of-determinant trace identity. Exact evaluation of (A.37), (A.40), (A.41), (A.42), and (A.44) gives:
| D | signs | D | signs | D | signs |
| 1 | 0 | 9 | ++000 | 17 | ++++++000 |
| 2 | 0 | 10 | +0000 | 18 | +++++0000 |
| 3 | 00 | 11 | +++000 | 19 | +++++++000 |
| 4 | 00 | 12 | ++0000 | 20 | ++++++0000 |
| 5 | +00 | 13 | ++++000 | 21 | ++++++++000 |
| 6 | 000 | 14 | +++0000 | 22 | +++++++0000 |
| 7 | +000 | 15 | +++++000 | 23 | +++++++++000 |
| 8 | +000 | 16 | ++++0000 |
The signs list the coefficients after the leading 1, in descending degree. For each computed coefficient, choose a positive denominator and inspect its integer numerator: + denotes a positive numerator and 0 denotes zero. Every coefficient is nonnegative. Hence
Since M is real symmetric, a negative eigenvalue would give a positive root of this polynomial. Therefore M\ge0, proving (A.25).
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