Effective joint equidistribution of rational points on expanding horospheres

In this talk, we study the behaviour of primitive rational points on expanding closed horospheres in the space of lattices. The equidistribution of these rational points is proved by Einsiedler, Mozes, Shah and Shapira (2016). Their proof uses techniques from homogeneous dynamics and relies particularly on measure-classification theorems due to Ratner. We pursue an alternative strategy based on Fourier analysis, Weil's bound for Kloosterman sums, recently proved bounds (by M. Erdélyi and Á. Tóth) for matrix Kloosterman sums, Roger's formula, and the spectral theory of automorphic functions. Our methods yield an effective estimate on the rate of convergence for a specific horospherical subgroup in any dimension. 

This is a joint work with D. El-Baz, B. Huang, J. Marklof and A. Strömbergsson.