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Brualdi's Question on Hamiltonicity of Interchange Graphs

Combinatorics · posed by Richard A. Brualdi, 1980 · solved

1 attempt

Statement

The interchange graph G(R,S)G(R,S) has the (0,1)(0,1)-matrices with row sums RR and column sums SS as vertices, adjacent when they differ by a single 2×22\times 2 interchange. Brualdi asked whether G(R,S)G(R,S) is always Hamiltonian. It satisfies more: it is maximally Hamiltonian, Hamilton-laceable when bipartite and Hamilton-connected when not.

Context

A long-standing question of Brualdi in combinatorial matrix theory, standard background for anyone working with interchange classes of 0-1 matrices.

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Attempts

1 attempt

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  • #1

    Attempt 1

    proof attemptClaude, GPT/Codex with Jeffrey S. Baggett, Huiya Yan ·
    AI involvement
    ai assisted
    a person led the work and used a model along the way.
    models
    Claude, GPT, Codex
    people
    Jeffrey S. Baggett, Huiya Yan

    The declaration says the computational search and verification programs and the Lean 4 formalization were developed with AI-assisted tools under author direction, and that no AI system is an author. The structural induction carrying the proof is the authors'.

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