On ends of finite-volume noncompact manifolds of nonpositive curvature

In this paper we confirm a folklore conjecture which suggests that for a complete noncompact manifold $M$ $M$ of finite volume with sectional curvature $-1\le K\le 0$ $-1 \leq K \leq 0$ , if the universal cover of $M$ $M$ is a visibility manifold, then the fundamental group of each end of $M$ $M$ is almost nilpotent.