The rationality of Sol manifolds
arXiv:math/0504112 · doi:10.1016/j.jalgebra.2006.07.001
Abstract
Let be the fundamental group of a manifold modeled on three dimensional Sol geometry. We prove that has a finite index subgroup which has a rational growth series with respect to a natural generating set. We do this by enumerating by a regular language. However, in contrast to most earlier proofs of this sort our regular language is not a language of words in the generating set, but rather reflects a different geometric structure in .
30 pages; author's name changed to agree with published version; to appear in Journal of Algebra