Exponential mixing and essential spectral gaps for Anosov subgroups (2408.11274v2)

Abstract: Let $\Gamma$ be a Zariski dense $\Theta$-Anosov subgroup of a connected semisimple real algebraic group for some nonempty subset of simple roots $\Theta$. In the Anosov setting, there is a natural compact metric space $\mathcal{X}$ equipped with a family of translation flows ${a^{\mathsf{v}}t}{t \in \mathbb R}$, parameterized by vectors $\mathsf{v}$ in the interior of the $\Theta$-limit cone $\mathcal{L}\Theta$ of $\Gamma$, which are conjugate to reparametrizations of the Gromov geodesic flow. We prove that for all $\mathsf{v}$ outside an exceptional cone $\mathscr{E} \subset \operatorname{int}\mathcal{L}\Theta$, which is a smooth image of the linear spans of the walls of the Weyl chamber, the translation flow is exponentially mixing with respect to the Bowen-Margulis-Sullivan measure associated to $\mathsf{v}$. Moreover, the exponential rate is uniform for a compact set of such vectors. We also obtain an essential spectral gap for the Selberg zeta function and a prime orbit theorem with a power saving error term. Our proof relies on Lie theoretic techniques to prove the crucial local non-integrability condition (LNIC) for the translation flows and thereby implement Dolgopyat's method in a uniform fashion. The exceptional cone $\mathscr{E}$ arises from the failure of LNIC for those vectors.