On exponential growth rates for free groups

Abstract

Let Fp be a free group of rank p ¸ 2. It is well-known that, with respect to a p-element generating set, that is, a basis, the exponential growth rate of Fp is 2p¡1. We show that the exponential growth rate ¿ of a group G with respect to a p-element generating set X is 2p¡1 if and only if G is free on X; otherwise ¿ < 2p¡1. rove that, for any ¯nite generating set X of Fp which is disjoint from X¡1, the exponential growth rate ¿ of Fp with respect to X is 2p ¡ 1 if and only if X is a basis of Fp; otherwise ¿ > 2p¡1.594