Logarithmic improvements in the Weyl law and exponential bounds on the number of closed geodesics are predominant

Abstract

Let $M$ be a smooth compact manifold of dimension $d$ without boundary. We introduce the concept of predominance for Riemannian metrics on $M$, a notion analogous to full Lebesgue measure which, in particular, implies density. We show that for a predominant metric, the number of closed geodesics of length smaller than $T$ has a stretched exponential upper bound in $T$. In addition, we study remainders in the Weyl law for predominant metrics. The Weyl law states that the number of Laplace-Beltrami eigenvalues smaller than ${\lambda }^2$ is asymptotic to $C{\lambda }^d$ with an $O({\lambda }^{d-1})$ error. We show that, for a predominant metric, the estimate on the error can by improved by a power of $\log \lambda$. After an application of recent results of the authors in the case of the Weyl law, these estimates follow from a study of the non-degeneracy properties of nearly closed orbits for predominant sets of metrics.