### Nattalie Tamam Tel Aviv University

Divergent trajectories in arithmetic homogeneous spaces of rational rank two Yeshiva University, 215 Lexington Ave, Room 312. The seminar has changed rooms.In the theory of Diophantine approximations, singular points are ones for which Dirichletâ€™s theorem can be infinitely improved. It is easy to see that all rational points are singular. In the special case of dimension one, the only singular points are the rational ones. In higher dimensions, points lying on a rational hyperplane are also obviously singular. However, in this case there are additional singular points. In the dynamical setting the singular points are related to divergent trajectories. In the talk I will define obvious divergent trajectories and explain the relation to rational points. In addition, I will present the more general setting involving Q-algebraic groups. Lastly I will discuss results concerning classification of divergent trajectories in Q-algebraic groups.