Strichartz estimates for the Schrödinger equation on compact manifolds with nonpositive sectional curvature

We obtain improved Strichartz estimates for solutions of the Schrödinger equation on compact manifolds with nonpositive sectional curvatures which are related to the classical universal results of Burq, Gérard and Tzvetkov [11]. More explicitly, we are able refine the arguments in the recent work of Blair and the authors [3] to obtain no-loss $L_t^p{L}_x^q$-estimates on intervals of length $\log \lambda \cdot {\lambda }^{-1}$ for all {\em admissible} pairs $(p,q)$ when the initial data have frequencies comparable to $\lambda$, which, given the role of the Ehrenfest time, is the natural analog in this setting of the universal results in [11]. We achieve this log-gain over the universal estimates by applying the Keel-Tao theorem along with improved global kernel estimates for microlocalized operators which exploit the geometric assumptions.