# Recurrence for smooth curves in the moduli space and application to the billiard flow on nibbled ellipses

## TL;DR

This paper establishes an effective recurrence criterion for smooth curves in the moduli space of translation surfaces and applies it to prove unique ergodicity of billiard flows in certain elliptical tables, answering a question by Zorich.

## Contribution

It provides a new recurrence criterion for smooth curves in the moduli space and demonstrates its application to billiard flows, showing unique ergodicity for almost every caustic.

## Key findings

- Almost every element in a smooth curve in the moduli space is recurrent.
- For almost every caustic in the billiard table, the flow is uniquely ergodic.
- The criterion is based on results by Minsky-Weiss and extends understanding of billiard dynamics.

## Abstract

In view of classical results of Masur and Veech almost every element in the moduli space of compact translation surfaces is recurrent. In this paper we focus on the problem of recurrence for elements of smooth curves in the moduli space. We give an effective criterion for the recurrence of almost every element of a smooth curve. The criterion relies on results developed by Minsky-Weiss in \cite{Mi-We}. Next we apply the criterion to the billiard flow on planar tables confined by arcs of confocal conics. The phase space of such billiard flow splits into invariant subsets determined by caustics. We prove that for almost every caustic the billiard flow restricted to the corresponding invariant set is uniquely ergodic. This answers affirmatively to a question raised by Zorich.