Hyperbolicity and Ergodicity in Randomly Perturbed Billiard Systems

Kien Nguyen; Hong-Kun Zhang

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arXiv · 2608.05484

Hyperbolicity and Ergodicity in Randomly Perturbed Billiard Systems

Kien Nguyen·Hong-Kun Zhang

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Abstract

In this paper, we investigate the Lyapunov exponents and hyperbolicity of random billiard systems under small stochastic perturbations. Our study begins with a review of the necessary theoretical background on Lyapunov exponents for stationary sequences of matrices and Markov processes. We then consider several classical billiard systems and demonstrate that random perturbations can lead to significant changes in their dynamical properties. Specifically, we show that non-circular elliptic and lemon billiards exhibit both ergodicity and hyperbolicity under random perturbations, whereas circular billiards, while ergodic, maintain zero Lyapunov exponents. We also establish conditions under which the largest Lyapunov exponent becomes positive, indicating the emergence of hyperbolic behavior in these systems. These results provide new insights into the stability and chaotic properties of dynamical systems subjected to random noise, with implications for the broader study of smooth dynamical systems.

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Kien Nguyen, Hong-Kun Zhang. 2026-08-06. Hyperbolicity and Ergodicity in Randomly Perturbed Billiard Systems. https://arxiv.org/abs/2608.05484

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