English

Asymptotic independence for random permutations from surface groups

Group Theory 2025-04-14 v3 Combinatorics Probability

Abstract

Let XX be an orientable hyperbolic surface of genus g2g\geq 2 with a marked point oo, and let Γ\Gamma be an orientable hyperbolic surface group isomorphic to π1(X,o)\pi_{1}(X,o). Consider the space Hom(Γ,Sn)\text{Hom}(\Gamma,S_{n}) which corresponds to nn-sheeted covers of XX with labeled fiber. Given γΓ\gamma\in\Gamma and a uniformly random ϕHom(Γ,Sn)\phi\in\text{Hom}(\Gamma,S_{n}), what is the expected number of fixed points of ϕ(γ)\phi(\gamma)? Formally, let Fn(γ)F_{n}(\gamma) denote the number of fixed points of ϕ(γ)\phi(\gamma) for a uniformly random ϕHom(Γ,Sn)\phi\in\text{Hom}(\Gamma,S_{n}). We think of Fn(γ)F_{n}(\gamma) as a random variable on the space Hom(Γ,Sn)\text{Hom}(\Gamma,S_{n}). We show that an arbitrary fixed number of products of the variables Fn(γ)F_{n}(\gamma) are asymptotically independent as nn\to\infty when there are no obvious obstructions. We also determine the limiting distribution of such products. Additionally, we examine short cycle statistics in random permutations of the form ϕ(γ)\phi(\gamma) for a uniformly random ϕHom(Γ,Sn)\phi\in\text{Hom}(\Gamma,S_{n}). We show a similar asymptotic independence result and determine the limiting distribution.

Keywords

Cite

@article{arxiv.2310.18637,
  title  = {Asymptotic independence for random permutations from surface groups},
  author = {Yotam Maoz},
  journal= {arXiv preprint arXiv:2310.18637},
  year   = {2025}
}

Comments

38 pages, 2 figures, Accepted for publication in Geometriae Dedicata

R2 v1 2026-06-28T13:04:32.926Z