Counterexamples to the xz-Conjecture and the Mathieu Conjecture for SU(2)

Christopher D. Long

The Laurent polynomial f(x,z)=(1−z⁻¹)((1−x)+xz) has zero pure product-integral moments for every positive n but marked moment (−1)^(n−1)/(n+1). It refutes xz(1,1), with padding for all mixed k,l≥1. Its SU(2) lift F=(1+c)(ad+b), G=−c has the same pure and marked Haar moments and refutes the SU(2) Mathieu conjecture.

Sources for this record

What was already known

The mixed xz cases and the SU(2) case remained open, although a separate Jacobian counterexample had already ruled out the universal compact-group conjecture.

AI involvement AI-centered

Long credits ChatGPT 5.6 Sol Pro with the witnesses, SU(2) lift, beta-binomial proof and parameter family. Long checked the identities, explained the mechanism and wrote the paper.

The model supplied the witnesses and symbolic proof during Long’s interactive research session.

Importance Notable

Explicit witnesses settle the mixed xz question and the SU(2) case.

Limitations

The reported Lean audit covers the core counterexamples and integration formula; two optional supporting derivations remain partial.

Technical verification Formal (Lean 4.34.0 with mathlib + human)

A reported Lean audit covers the core xz and SU(2) statements, and Long checked the displayed identities.

Independent checking

independent human algebraic verification

Checker
Christopher D. Long
Scope
Displayed xz and SU(2) moment identities
Basis
Reported by the linked checker
Evidence source

Formal checking

proof assistant build, theorem-to-manuscript correspondence ledger and transitive-axiom audit

Checker
Lean 4 kernel via the author's formalization repository
Scope
Theorem 2.1, Corollary 2.2, Proposition 3.1, Lemma 4.1 and Theorem 4.2, including actual SU(2) Haar moments
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

Long explains the beta-binomial cancellation and transfer to SU(2).

Correction and publication history

2026-10-18 · publication

The same explicit witness connects the mixed xz and SU(2) cases; they form one claim group and do not duplicate the earlier Jacobian result.

Read this published revision