Equidistribution of divergent orbits of the diagonal group in the space of lattices

Abstract: We consider divergent orbits of the group of diagonal matrices in the space of lattices in Euclidean space. We define two natural numerical invariants of such orbits: The discriminant - an integer - and the type - an integer vector. We then study the question of the limit distributional behaviour of these orbits as the discriminant goes to infinity. Using entropy methods we prove that for divergent orbits of a specific type, virtually any sequence of orbits equidistribute as the discriminant goes to infinity. Using measure rigidity for higher rank diagonal actions we complement this result and show that in dimension 3 or higher only very few of these divergent orbits can spend all of their life-span in a given compact set before they diverge.