An algorithm that decides translation equivalence in a free group of rank two

Abstract

Let F_2 be a free group of rank 2. We prove that there is an algorithm that decides whether or not, for given two elements u, v of F_2, u and v are translation equivalent in F_2, that is, whether or not u and v have the property that the cyclic length of phi(u) equals the cyclic length of phi(v) for every automorphism phi of F_2. This gives an affirmative solution to problem F38a in the online version (http://www.grouptheory.info) of [1] for the case of F_2.