A counterexample to the Foregger-Sinkhorn tie-point conjecture

Yair Lavi

An explicit 8×8 nearly decomposable support has a unique global permanent minimizer on its full doubly stochastic face. At a specified zero, the permanental cofactor exceeds the permanent although that zero is not a tie point, refuting the Foregger–Sinkhorn implication.

Sources for this record

What was already known

Foregger and Sinkhorn proposed the implication in 1986. A special complex or multiplex family had been checked, but no earlier general counterexample was identified.

AI involvement AI-led

Yair Lavi credits GPT-5.6 Sol and Claude Fable 5 with proving the counterexample under his guidance. He reviewed the resulting arguments and took responsibility for the final paper.

The author attributes the proof of the counterexample theorem to the two models under his guidance.

Importance Notable

Provides a counterexample to a long-standing named conjecture about permanent minimizers.

Limitations

The paper does not show that eight is the smallest counterexample dimension. The author reports reviewing the proof arguments but does not specify whether that review covered every global-minimum and cofactor step.

Technical verification Partial

Lavi reports reviewing the AI-derived proof arguments for Theorem 1, but does not say that he completed a rigorous check of the full global-minimum and cofactor calculations. The documented review supports a human check of unspecified scope; a complete check is not established.

Independent checking

Author review of AI-derived proof arguments; precise coverage not stated

Checker
Yair Lavi, author
Scope
Theorem 1 order-eight counterexample to the tie-point implication
Basis
Reported by the linked checker
Evidence source

Human understanding Few

A human proof review is reported, but no distinct account by Lavi explains the central AI-derived minimization mechanism. Few is the evidence default, not a claim of inability.

Correction and publication history

2026-10-18 · publication

Provides a counterexample to a long-standing named conjecture about permanent minimizers.

Read this published revision