Deformation of finite-volume hyperbolic Coxeter polyhedra, limiting   growth rates and Pisot numbers
  A connection between real poles of the growth functions for Coxeter groups acting on hyperbolic space of dimensions three and greater and algebraic integers is investigated. In particular, a geometric convergence of fundamental domains for cocompact hyperbolic Coxeter groups with finite-volume limiting polyhedron provides a relation between Salem numbers and Pisot numbers. Several examples conclude this work. 
Alexander Kolpakov
math.MG math.CO