{ "id": "math/0407345", "version": "v1", "published": "2004-07-20T18:53:37.000Z", "updated": "2004-07-20T18:53:37.000Z", "title": "Distribution of lattice orbits on homogeneous varieties", "authors": [ "Alexander Gorodnik", "Barak Weiss" ], "categories": [ "math.DS" ], "abstract": "Given a lattice \\Gamma in a locally compact group G and a closed subgroup H of G, one has a natural action of \\Gamma on the homogeneous space V=H\\G. For an increasing family of finite subsets {\\Gamma_T: T>0}, a dense orbit v\\Gamma, v\\in V, and compactly supported function \\phi on V, we consider the sums S_{\\phi,v}(T)=\\sum_{\\gamma\\in \\Gamma_T} \\phi(v \\gamma). Understanding the asymptotic behavior of S_{\\phi,v}(T) is a delicate problem which has only been considered for certain very special choices of H, G and {\\Gamma_T}. We develop a general abstract approach to the problem, and apply it to the case when G is a Lie group and either H or G is semisimple. When G is a group of matrices equipped with a norm, we have S_{\\phi,v}(T) \\sim \\int_{G_T} \\phi(vg) dg, where G_T={g\\in G:||g||