Lyapunov exponents for open billiard systems

In this thesis, we investigate the largest Lyapunov exponent for open billiards in both two- and higherdimensional Euclidean spaces. In R2, we estimate the largest Lyapunov exponent 1 for open billiards, demonstrating its continuity and di↵erentiability with respect to a small perturbation parameter ↵. Extending this study to Rn for n 3, we prove similar results for the largest Lyapunov exponent for open billiards in higher dimensions. Additionally, we consider the billiard flow in the exterior of several (at least three) balls in R3 with centres lying on a plane. We assume that the balls satisfy the no-eclipse condition (H) and their radii are small compared to the distances between their centres. We prove that with respect to any Gibbs measure on the non-wandering set of the billiard map, the two positive Lyapunov exponents are di↵erent: 1 > 2 > 0. These findings enhance our understanding of chaotic dynamics and could be applied to similar physical systems, such as Lorentz gases.