Reidemeister classes, wreath products and solvability

Abstract

Reidemeister (or twisted conjugacy) classes are considered in restricted wreath products of the form $G\wr {\mathbb{Z}}^k$, where $G$ is a finite group. For an automorphism $\phi$ of finite order (supposed to be the same for the torsion subgroup $\oplus G$ and the quotient ${\mathbb{Z}}^k$) with finite number $R(\phi )$ of Reidemeister classes, this number is identified with the number of equivalence classes of finite-dimensional unitary irreducible representations of the product that are fixed by the dual homeomorphism $\hat{\phi }$ (i.e. the so-called conjecture TBFT${}_f$ is proved in this case). For these groups and automorphisms, we prove the following conjecture: if a finitely generated residually finite group has an automorphism with $R(\phi )<\infty$ then it is solvable-by-finite (so-called conjecture R).

V3: many changes, an incorrect example removed, new theorem added