Typical hyperbolic surfaces have an optimal spectral gap

Fuente: arXiv
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Main Author: Monk, Laura
Format: Preprint
Published: 2026
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author Monk, Laura
author_facet Monk, Laura
contents The first non-zero Laplace eigenvalue of a hyperbolic surface, or its spectral gap, measures how well-connected the surface is: surfaces with a large spectral gap are hard to cut in pieces, have a small diameter and fast mixing times. For large hyperbolic surfaces (of large area or large genus $g$, equivalently), we know that the spectral gap is asymptotically bounded above by $\frac 14$. The aim of these talks is to present joint work with Nalini Anantharaman, where we prove that most hyperbolic surfaces have a near-optimal spectral gap. That is to say, we prove that, for any $ε> 0$, the Weil--Petersson probability for a hyperbolic surface of genus $g$ to have a spectral gap greater than $\frac 14- ε$ goes to one as $g$ goes to infinity. This statement is analogous to Alon's 1986 conjecture for regular graphs, proven by Friedman in 2003. I will present our approach, which shares many similarities with Friedman's work, and introduce new tools and ideas that we have developed in order to tackle this problem.
format Preprint
id arxiv_https___arxiv_org_abs_2601_15157
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Typical hyperbolic surfaces have an optimal spectral gap
Monk, Laura
Spectral Theory
Metric Geometry
Primary 58J50, 32G15. Secondary 05C80, 11F72
The first non-zero Laplace eigenvalue of a hyperbolic surface, or its spectral gap, measures how well-connected the surface is: surfaces with a large spectral gap are hard to cut in pieces, have a small diameter and fast mixing times. For large hyperbolic surfaces (of large area or large genus $g$, equivalently), we know that the spectral gap is asymptotically bounded above by $\frac 14$. The aim of these talks is to present joint work with Nalini Anantharaman, where we prove that most hyperbolic surfaces have a near-optimal spectral gap. That is to say, we prove that, for any $ε> 0$, the Weil--Petersson probability for a hyperbolic surface of genus $g$ to have a spectral gap greater than $\frac 14- ε$ goes to one as $g$ goes to infinity. This statement is analogous to Alon's 1986 conjecture for regular graphs, proven by Friedman in 2003. I will present our approach, which shares many similarities with Friedman's work, and introduce new tools and ideas that we have developed in order to tackle this problem.
title Typical hyperbolic surfaces have an optimal spectral gap
topic Spectral Theory
Metric Geometry
Primary 58J50, 32G15. Secondary 05C80, 11F72
url https://arxiv.org/abs/2601.15157