Almost-primes in horospherical flows on the space of lattices

Abstract: We study the asymptotic distribution of almost-prime entries of abelian horospherical flows on {\Gamma}\SL(n,R), where {\Gamma} is either SL(n,Z) or a cocompact lattice. In the cocompact case, we obtain a result that implies density of almost-primes of a sufficient order, and in the space of lattices we show the density of almost-primes in the orbits of points satisfying a certain Diophantine condition. Along the way we give an effective equidistribution result for arbitrary horospherical flows on the space of lattices, as well as an effective rate for the equidistribution of arithmetic sequences of times in abelian horospherical flows.