We consider a nonlinear area preserving Anosov map $M$ on the torus phase space, which is the simplest example of a fully chaotic dynamics. We are interested in the quantum dynamics for long time, generated by the unitary quantum propagator $\widehat{M}$. The usual semi-classical Trace formula expresses $Tr\left({\widehat{M}}^t\right)$ for finite time $t$, in the limit $\hslash \to 0$, in terms of periodic orbits of $M$ of period $t$. Recent work reach time $t\ll t_E/6$ where $t_E=log(1/\hslash )/\lambda$ is the Ehrenfest time, and $\lambda$ is the Lyapounov coefficient. Using a semi-classical normal form...

We present a new method for establishing the ‘‘gap” property for finitely generated subgroups of $SU\left(2\right)$, providing an elementary solution of Ruziewicz problem on $S^2$ as well as giving many new examples of finitely generated subgroups of $SU\left(2\right)$ with an explicit gap. The distribution of the eigenvalues of the elements of the group ring $𝐑[SU(2\left)\right]$ in the $N$-th irreducible representation of $SU\left(2\right)$ is also studied. Numerical experiments indicate that for a generic (in measure) element of $𝐑[SU(2\left)\right]$, the “unfolded” consecutive spacings...

We investigate the spectral distribution of the damped wave equation on a compact Riemannian manifold, especially in the case of a metric of negative curvature, for which the geodesic flow is Anosov. The main application is to obtain conditions (in terms of the geodesic flow on $X$ and the damping function) for which the energy of the waves decays exponentially fast, at least for smooth enough initial data. We review various estimates for the high frequency spectrum in terms of dynamically defined...