arXiv:2606.03472v2

Planes in quadratic 4-space and associated shapes of lattices

Menny Aka, Konstantin Andritsch, Andreas Wieser

math.NT37A1711E1611G1511H55

Abstract

Let Q=x12x22x32+x42Q=-x_1^2-x_2^2-x_3^2+x_4^2 be the standard signature (1,3)(1,3) quadratic form. To each non-degenerate rational plane LL in the four-dimensional quadratic space (Q4,Q)(\mathbb{Q}^4,Q) we can naturally attach a periodic geodesic on the Bianchi orbifold SL2(Z[i])\H3\mathrm{SL}_2(\mathbb{Z}[i])\backslash \mathbb{H}^3 which records the position of LL in the Grassmannian up to integer rotations. Moreover, each such plane LL defines a CM point and a periodic geodesic on the modular curve through restriction of QQ to LL and its orthogonal complement. Lastly, the local isomorphism between SO1,3(R)\mathrm{SO}_{1,3}(\mathbb{R}) and SL2(C)\mathrm{SL}_2(\mathbb{C}) gives rise to a further periodic geodesic on the Bianchi orbifold. In this article, we exhibit a natural coupling of all the above objects and prove simultaneous equidistribution under a Linnik-type splitting condition. The main ingredient is the classification of joinings of higher-rank diagonalizable actions on homogeneous spaces due to Einsiedler and Lindenstrauss.

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Audited against arXiv v2

Not a correctness certificate. A “Correct” result may include yellow typos or minor formal corrections that do not affect substantive soundness. It means this audit found no unresolved substantive error under the stated criteria; it does not replace expert scrutiny or formal verification.

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Detailed mathematical audit

Generated August 18, 2026
01Statements2 reported findingsContains unsupported statements

The simultaneous equidistribution theorem under the square-free, odd, and auxiliary splitting hypotheses is verified. The separately stated Duke-type theorem for all nonsquare discriminants is not proved in the manuscript and is not obtained by projecting the simultaneous theorem, whose range of discriminants is strictly narrower. No counterexample to that Duke-type statement was found.

Theorem 1.2Correct

Simultaneous equidistribution of the four coupled objects

Pages 5 and 25–36 · Theorems 1.2 and 4.3 · arXiv:2606.03472v2

The adelic torus packet projects to the claimed coupled measure through Propositions 4.4 and 4.7. The individual factors equidistribute by the class-group estimates and the toric equidistribution input. At the auxiliary prime, the splitting condition supplies a second class-A\mathcal A' direction; the Einsiedler--Lindenstrauss joining classification then leaves only the product Haar measure, since the possible graph joinings are ruled out by the nonisomorphic factors or by the incompatible weights asa_s and a2sa_{2s}. The sequential form of Theorem 4.3 is uniform over the finitely many collections at each discriminant, so the final convex-combination argument is valid.

Theorem 1.1Not able to verify

Duke-type equidistribution for all nonsquare discriminants

Page 3 · Theorem 1.1 · arXiv:2606.03472v2

The theorem claims equidistribution of the full periodic-geodesic packet as DD\to\infty through every nonsquare DD. After its statement, the manuscript does not return to Theorem 1.1, give a proof, or cite an external theorem with this exact scope. Projection of Theorem 1.2 proves only the subsequences for which DD is odd and square-free and either DD or D-D is a nonzero square modulo a fixed odd prime. The toric-period method sketched later suggests a possible independent proof, but the paper does not verify the required order, packet, discriminant, and volume comparison for arbitrary nonsquare DD. Therefore the printed text does not support the full statement. This is an omitted proof obligation, not evidence that the theorem is false.

02Proofs4 reported findingsContains incorrect or incomplete proofs

The Clifford-algebra construction and the main simultaneous-equidistribution chain are correct and complete at the stated level of reliance on standard toric-period and joining theorems. Theorem 1.1 has no proof or exact cited substitute, leaving one central statement unsupported. Several cross-references say “Theorem” where the referenced item is a lemma; these are harmless typos.

Theorem 1.1Incomplete as written

No proof is supplied for the all-nonsquare Duke-type theorem

Page 3, followed by Sections 2–5 · arXiv:2606.03472v2

A search through the complete manuscript finds no proof of Theorem 1.1 after its introductory statement. The proof of Theorem 1.2 explicitly assumes odd square-free discriminants and a local splitting condition, so it cannot serve as the missing argument. A repair requires either a precise reference proving equidistribution for the particular Bianchi geodesic packet attached to every nonsquare DD, or an added argument identifying that packet with the relevant adelic torus orbits and checking that their discriminants and volumes satisfy the toric equidistribution hypotheses as DD\to\infty.

Theorem 4.3 and deduction of Theorem 1.2Correct and complete

Adelic packet, marginal equidistribution, and joining classification

Pages 25–36 · Sections 4–5 · arXiv:2606.03472v2

The integral-plane reconstruction preserves discriminant and identifies the three associated binary forms. The class-group maps have only Do(1)D^{o(1)} index, which is within the volume threshold of Theorem 5.5. The limiting measure has Haar marginals, the real and pp-adic actions meet the higher-rank hypotheses, and the algebraic alternatives in every pair of factors are correctly eliminated. Finally, Proposition 4.7 identifies the projected packet with the average of the geometric measures, giving Theorem 1.2.

Theorem 5.5Correct and complete

Toric subcollection equidistribution input

Pages 32–34 · Theorem 5.5 and proof · arXiv:2606.03472v2

The lower volume bound limits the index of the subcollection to a small power of the torus discriminant. Finite Fourier expansion reduces its characteristic function, and the square-map restriction, to finitely many toric characters. Waldspurger's formula, uniform GL2\mathrm{GL}_2 subconvexity, and local toric-integral bounds give a fixed power saving once the theorem's δ\delta is chosen below that saving. The cited Clozel--Ullmo analysis also treats Eisenstein contributions, so the noncompact quotient does not leave an unaddressed continuous-spectrum case.

Clozel–Ullmo, Equidistribution de mesures algébriques
Cross-references in Sections 4–5Typo

Several lemmas are called theorems

Pages 29–34 · references to 3.3, 4.5, 4.7, 5.2, 5.3, and 5.4 · arXiv:2606.03472v2

The cited numbered results are printed as Lemmas 3.3, 4.5, 5.2, 5.3, and 5.4 and Proposition 4.7, although the prose repeatedly calls them theorems. The intended references are uniquely determined by their numbers and content, so these naming mismatches do not affect any deduction.

03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:2606.03472v2
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Menny Aka, Konstantin Andritsch, Andreas Wieser
Audit date
August 18, 2026
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