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Metadata 
slug: kade-2025-box-six-vertex-determinant-refutation
bibkey: kade2025boxsixvertex
doi: 10.18452/33769
url: https://arxiv.org/abs/2509.03416v1
triage: theorem
motivation_gids:
  - D5/S3/StatisticalMechanics/VertexModels/KadeBoxBoundaryRefutation.result

The box partition function of the six-vertex model

Problem

Kade (arXiv:2509.03416v1, section 2.3) puts the six-vertex model in a square box with arrow-reflecting walls: 2M horizontal spectral lines, in pairs x_i, 1/x_i, run from the right wall to the left wall, and 2M vertical lines, in pairs y_j, 1/y_j, run from the top wall to the bottom wall. The bulk weights are a = p t − 1/(p t), b = t − 1/t, c = p − 1/p with t = x/y, and the walls carry the diagonal K-matrices K_L(x) = diag(b(xξ_L), b(x/(qξ_L))), K_R(x) = diag(b(xξ_R), b(xq/ξ_R)), K_U(y) = diag(b(yξ_U), b(yq/ξ_U)), K_D(y) = diag(b(yξ_D), b(y/(qξ_D))). The thesis proposes

Z_M({x_i}|{y_i}) = ∏{i,j} (x_i/y_j − y_j/x_i) W(x_i, y_j) / ∏{i<j} (x_j/x_i − x_i/x_j)(y_i/y_j − y_j/y_i) · det[ c² a(x_i y_j) a(1/(x_i y_j)) F^LU(x_i) F^DR(y_j) / ((x_j/y_i − y_i/x_j) W(x_i, y_j)) ]

with W(x, y) = a(xy) a(1/(xy)) a(x/y) a(y/x), F^LU(x) = b(xξ_L) b(xq/ξ_U) + b(x/(qξ_L)) b(xξ_U) and F^DR(y) = b(yξ_D) b(yq/ξ_R) + b(y/(qξ_D)) b(yξ_R), and its concluding chapter says that the conjecture “has to be proven or discarded”.

Issue #10444 fixes the readings: the absolute arrow conventions of the six vertices and of the diagonal wall components are those of the thesis’s figures (6Vvertices, KLeft_mat, KRight_mat, KUp_mat, KDown_mat); rows carry x_1, 1/x_1, x_2, 1/x_2, … from the top and columns y_1, 1/y_1, … from the left; q is the crossing parameter p, the only value among those tried at which the 2 × 1 box partition function is symmetric in its two horizontal spectral parameters, as integrability requires; the parameters are complex and the formula is asserted wherever none of its printed denominators vanishes.

Motivation

The six-vertex model is the square-ice model of statistical mechanics, and the box boundary conditions are an integrable way to close the lattice on all four sides; a closed determinant for the box partition function would play the role of the Izergin–Korepin determinant for domain-wall boundaries. The frozen declaration D5/S3/StatisticalMechanics/VertexModels/KadeBoxBoundaryRefutation.result shows that the proposed determinant is already wrong for the smallest box.

Gap

Issue #10444 preregisters the statement, the readings and the counterexample before any formalization. The arXiv API lists only v1 (2025-09-03). Web searches for box boundary conditions of the six-vertex model found only domain-wall and single reflecting-end results. These readings are not-found-in-searched-scope; they do not establish an exhaustive worldwide literature search or priority.

Route

  1. At M = 1 both products in the prefactor are over a single pair or empty, and the determinant is the single entry, so the formula reads (x/y − y/x) W(x, y) · c² a(xy) a(1/(xy)) F^LU(x) F^DR(y) / ((x/y − y/x) W(x, y)).
  2. At p = 2, x = 2, y = 3 and all four boundary parameters 1, W(2, 3) = −4004/81 and 2/3 − 3/2 = −5/6 are nonzero and the formula gives −7150.
  3. The partition function of the 1 × 1 box, the sum over the 2^12 configurations of arrows on the twelve edge segments of the product of the four wall weights and the four crossing weights, is −400400/81 at this point.

Falsifier

A reading of the arrow conventions, of the line parameters or of q under which the formula holds at M = 1 would undo the refutation. Among the sixteen labelings of the wall states, both orientations of the crossing ratio and q ∈ {p, 1/p, 5/11}, the twenty-four combinations that satisfy the thesis’s recursion at x = y all violate the formula at x ≠ y.

Evidence

An independent exact computation over the rationals reproduces the thesis’s recursion Z_1|_{x=y} = c² a(x²) a(x^{−2}) F^LU(x) F^DR(x) under the figure conventions and gives Z_1 = −400400/81 against the formula’s −7150 at the point above. Arranging Z_1 as a 4 × 4 matrix over the (left, top) wall states and the (bottom, right) wall states gives rank 4 at (p, x, y) = (2, 2, 3) and (7/5, 13/4, 5/9), while the formula corresponds to a rank-one matrix.

The canonical source is D5/S3/StatisticalMechanics/VertexModels/KadeBoxBoundaryRefutation.lean. Its public declarations are HArrow, VArrow, a, b, c, vertexWeight, leftWall, rightWall, topWall, bottomWall, rowParam, colParam, Z, W, FLU, FDR, formula, claim, and result. The frozen module state has statement identity sha256:0f601c5f1faf3c63e3f6dd8c3724b23f2df5afb8d82eb4f6994c349d3664bcaf. The result declaration has statement identity sha256:7af843566fe215ba6bc10924ede01da51151820b4748bbbc50a0d9829b4ef044. The Freeze event is sha256:bf8503b8cc172add2c1e9568e142ee8c4395c144d5c7bb57b047f14dc24f5a3e and has no project-level frozen prerequisites. The proof uses only the standard axioms propext, Classical.choice and Quot.sound; no sorry, native_decide, or new axiom.

Triage

theorem; resolution refuted, for the conjecture as read in #10444. The public theorem has proof_shape: content: the kernel evaluation of the box partition function over the rationals and its transfer to the complex numbers through the rational cast are new propositions on the live path of the proof. admission_basis: open-problem-resolution under preregistration issue #10444; utility kind=certified-instance; basis=refutes with typed claim and result. There is no atom and no digestion coverage edge.

ASSUMED-UNVERIFIED

The arrow conventions of the wall components are read from the thesis’s figures; the thesis does not state q in section 2.3, and q = p rests on the symmetry check above. The bounded literature check does not establish exhaustive worldwide novelty, priority, or the absence of an independent refutation.