On density of infinite subsets II: Dynamics on homogeneous spaces

Abstract:

Let $G$ be a noncompact semisimple Lie group, let $\Gamma$ be an irreducible cocompact lattice in $G$, and let $P<G$ be a minimal parabolic subgroup. We consider the dynamics of $P$ acting on $G/\Gamma$ by left translation. For any infinite subset $A\subset G/\Gamma$, we show that, for any $\epsilon >0$, there is a $g\in P$ such that $gA$ is $\epsilon$-dense. We also prove a similar result for certain discrete group actions on $\mathbb T^n$.