Nielsen Equivalence In Gupta-Sidki Groups

For a group G generated by k elements, the Nielsen equivalence classes are defined as orbits of the action of AutF(k), the automorphism group of the free group of rank k, on the set of generating k-tuples of G. Let p >= 3 be prime and G(p) the Gupta-Sidki p-group. We prove that there are infinitely many Nielsen equivalence classes on generating pairs of G(p).