Limit-profile conjecture for the strictly biased random transposition shuffle

From papers

Let PP be the transition matrix of the biased random transposition shuffle on NN cards, let UU be the uniform distribution on permutations, let dTVd_{\operatorname{TV}} denote total variation distance, and let Poiss(λ)\operatorname{Poiss}(\lambda) denote the Poisson distribution with mean λ\lambda. For cRc \in \mathbb{R} and b<1b<1, consider the shuffle after 12bN(logNc)\frac{1}{2b}N(\log N-c) steps. Limit-profile conjecture. The total variation distance satisfies

dTV(P12bN(logNc),U)dTV(Poiss(1+ec2),Poiss(1)),as N.d_{\operatorname{TV}}\left(P^{\frac{1}{2b}N(\log N-c)},U\right)\to d_{\operatorname{TV}}\left(\operatorname{Poiss}\left(1+\frac{e^c}{2}\right),\operatorname{Poiss}(1)\right),\qquad\text{as }N\to\infty.

This conjectures a cutoff limit profile for the strictly biased random transposition shuffle, based on the limiting distribution of the number of fixed cards. It contrasts with the unbiased random-transposition case, where the corresponding limiting Poisson mean is 1+ec1+e^c; the claimed profile remains unproved in the source.

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Sources & referencesView supporting material

Primary source

Evita Nestoridi and Alan Yan, “Cutoff for the Biased Random Transposition Shuffle”, arXiv:2409.16387 (2024).

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