Mixing asymptotics for time-changes of horocycle flows

Fuente: arXiv
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Autor principal: Ravotti, Davide
Formato: Preprint
Publicado: 2025
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author Ravotti, Davide
author_facet Ravotti, Davide
contents Mixing-via-shearing is a powerful and versatile method for establishing mixing properties of smooth parabolic flows. In its quantitative form, it provides upper bounds on the decay of correlations for sufficiently smooth observables. Despite its wide applicability, determining the exact rates of mixing for a given smooth parabolic flow remains notoriously difficult. Apart from the classical horocycle flow, no examples are known where polynomial asymptotics, or sharp lower bounds, hold. In this paper, we address this question for smooth time-changes of horocycle flows on compact hyperbolic surfaces. Our approach relies on a refined version of the mixing-via-shearing method which leverages on a precise description of the ergodic integrals for horocycle flows, in particular of the regularity of the coefficients appearing in their asymptotic expansions. Using this method, we prove polynomial upper bounds on the decay of correlations for smooth observables that match the optimal rates originally obtained by Ratner for the standard horocycle flow. Furthermore, in the presence of a spectral gap below $1/4$, we establish exact polynomial asymptotics, mirroring the classical behavior of the horocycle flow.
format Preprint
id arxiv_https___arxiv_org_abs_2512_01488
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Mixing asymptotics for time-changes of horocycle flows
Ravotti, Davide
Dynamical Systems
Mixing-via-shearing is a powerful and versatile method for establishing mixing properties of smooth parabolic flows. In its quantitative form, it provides upper bounds on the decay of correlations for sufficiently smooth observables. Despite its wide applicability, determining the exact rates of mixing for a given smooth parabolic flow remains notoriously difficult. Apart from the classical horocycle flow, no examples are known where polynomial asymptotics, or sharp lower bounds, hold. In this paper, we address this question for smooth time-changes of horocycle flows on compact hyperbolic surfaces. Our approach relies on a refined version of the mixing-via-shearing method which leverages on a precise description of the ergodic integrals for horocycle flows, in particular of the regularity of the coefficients appearing in their asymptotic expansions. Using this method, we prove polynomial upper bounds on the decay of correlations for smooth observables that match the optimal rates originally obtained by Ratner for the standard horocycle flow. Furthermore, in the presence of a spectral gap below $1/4$, we establish exact polynomial asymptotics, mirroring the classical behavior of the horocycle flow.
title Mixing asymptotics for time-changes of horocycle flows
topic Dynamical Systems
url https://arxiv.org/abs/2512.01488