Comparability of random permutations in the strong Bruhat order

Fuente: arXiv
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Autores principales: Christo, Nicholas, Michelen, Marcus
Formato: Preprint
Publicado: 2026
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author Christo, Nicholas
Michelen, Marcus
author_facet Christo, Nicholas
Michelen, Marcus
contents The (strong) Bruhat order for permutations provides a partial ordering defined as follows: two permutations are comparable if one can be obtained from the other by a sequence of adjacent transpositions that each increase the number of inversions by $1$. Given two random permutations, what is the probability that they are comparable in the Bruhat order? This problem was first considered in a 2006 work of Hammett and Pittel, which showed an exponential lower bound and a polynomial upper bound. The lower bound was very recently improved to the subexponential bound of $\exp(-n^{1/2 + o(1)})$ by Boretsky, Cornejo, Hodges, Horn, Lesnevich, and McAllister. Hammett and Pittel predicted that the probability should decrease polynomially. We show that the probability decreases faster than any polynomial and is on the order of $\exp(-Θ(\log^2 n))$.
format Preprint
id arxiv_https___arxiv_org_abs_2602_16625
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Comparability of random permutations in the strong Bruhat order
Christo, Nicholas
Michelen, Marcus
Combinatorics
The (strong) Bruhat order for permutations provides a partial ordering defined as follows: two permutations are comparable if one can be obtained from the other by a sequence of adjacent transpositions that each increase the number of inversions by $1$. Given two random permutations, what is the probability that they are comparable in the Bruhat order? This problem was first considered in a 2006 work of Hammett and Pittel, which showed an exponential lower bound and a polynomial upper bound. The lower bound was very recently improved to the subexponential bound of $\exp(-n^{1/2 + o(1)})$ by Boretsky, Cornejo, Hodges, Horn, Lesnevich, and McAllister. Hammett and Pittel predicted that the probability should decrease polynomially. We show that the probability decreases faster than any polynomial and is on the order of $\exp(-Θ(\log^2 n))$.
title Comparability of random permutations in the strong Bruhat order
topic Combinatorics
url https://arxiv.org/abs/2602.16625