Caputo's shuffle spectral gap conjecture

About 13 years old · traced to

Let nn be a positive integer with n≥3n\ge 3. For each A⊂{1,…,n}A\subset\{1,\ldots,n\}, let Sn,AS_{n,A} be the set of permutations in SnS_n fixing every element outside AA, and define

Jn,A:=∑π∈Sn,Aπ.J_{n,A}:=\sum_{\pi\in S_{n,A}}\pi.

For nonnegative coefficients αA\alpha_A, set

w=∑A⊂{1,…,n}αAJn,A.w=\sum_{A\subset\{1,\ldots,n\}}\alpha_AJ_{n,A}.

Let supp⁡w\operatorname{supp}w denote the support of ww, and let ψSn(w)\psi_{S_n}(w) be the spectral gap of ww, while ψSn(w,D)\psi_{S_n}(w,\mathsf D) is the spectral gap in the representation D\mathsf D. Caputo's conjecture. If supp⁡w\operatorname{supp}w generates SnS_n, then

ψSn(w)=ψSn(w,D).\psi_{S_n}(w)=\psi_{S_n}(w,\mathsf D).

This conjecture was communicated privately by P. Caputo, and the source reports that it resisted both proof attempts and numerical disproof; no resolution is supplied.

References

Primary source

Filippo Cesi, “A few remarks on the octopus inequality and Aldous' spectral gap conjecture”, arXiv:1310.6156 (2013).

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