Bapat–Sunder's largest-eigenvalue conjecture for the permanent matrix

From papers

Let Hn\mathcal{H}_n be the set of n×nn\times n positive semidefinite Hermitian matrices. For A=[ai,j]HnA=[a_{i,j}]\in\mathcal{H}_n, let A(i,j)A(i,j) be the submatrix obtained by deleting row ii and column jj, and define FA=[fi,j]F_A=[f_{i,j}] by

fi,j=ai,jper(A(i,j)).f_{i,j}=a_{i,j}\operatorname{per}(A(i,j)).

Bapat–Sunder's conjecture. The largest eigenvalue of FAF_A should satisfy

λmax(FA)per(A).\lambda_{\max}(F_A)\leq \operatorname{per}(A).

Equivalently, per(A)\operatorname{per}(A) should be the largest eigenvalue of FAF_A. Drury disproved this conjecture, so it is refuted.

Progress summary

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Sources & referencesView supporting material

Primary source

Léo Pioge, Kamil K. Pietrasz, Benoit Seron, Leonardo Novo and Nicolas J. Cerf, “A logical implication between two conjectures on matrix permanents”, arXiv:2508.00111 (2025).

Additional references

2 papers in this index state this conjecture (2022–2025). The statement above is taken from the most recent of them; the others are arXiv:2202.01867.

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