Asymptotic density of rational sets in free abelian groups
  In this paper we study asymptotic density of rational sets in free abelian group $\mathbb{Z}^n$ of rank $n$. We show that any rational set $R$ in $\mathbb{Z}^n$ has asymptotic density. If $R$ is given by its semi-simple decomposition we show how to compute its asymptotic density. 
Anton Menshov
math.GR