Rank gradient and p-gradient of amalgamated free products and HNN extensions
arXiv:1309.3806
Abstract
We calculate the rank gradient and p-gradient of free products, free products with amalgamation over an amenable subgroup, and HNN extensions with an amenable associated subgroup. The notion of cost is used to compute the rank gradient of amalgamated free products and HNN extensions. For the p-gradient the Kurosh subgroup theorems for amalgamated free products and HNN extensions will be used.
Cost of restricted action result has been strengthened. Proofs of main results have been shortened and altered. Article length has been shortened