Let G be a real Lie group, Λ < G a lattice and H G a connected semisimple subgroup without compact factors and with finite center. We define the notion of H-expanding measures µ on H and, applying recent work of Eskin-Lindenstrauss, prove that µ-stationary probability measures on G/Λ are homogeneous. Transferring a construction by Benoist-Quint and drawing on ideas of Eskin-Mirzakhani-Mohammadi, we construct Lyapunov/Margulis functions to show that H-expanding random walks on G/Λ satisfy a recurrence condition and that homogeneous subspaces are repelling. Combined with a countability result, this allows us to prove equidistribution of trajectories in G/Λ for H-expanding random walks and to obtain orbit closure descriptions. Finally, elaborating on an idea of Simmons-Weiss, we deduce Birkhoff genericity of a class of measures with respect to some diagonal flows and extend their applications to Diophantine approximation on similarity fractals to a non-conformal and weighted setting.
Contents1. Introduction 1 2. H-expansion: Definition and basic properties 11 3. Examples of H-expanding measures 14 4. Measure rigidity 22 5. Countability of homogeneous subspaces 28 6. Height functions with contraction properties 31 7. Recurrence, equidistribution, topology of homogeneous measures 41 8. Birkhoff genericity 45 9. Connections to Diophantine approximation on fractals 50 Appendix A. Epimorphic subgroups and subalgebras 55 References 57