On the residual finiteness of outer automorphisms of relatively hyperbolic groups

Abstract

We show that every virtually torsion-free subgroup of the outer automorphism group of a conjugacy separable relatively hyperbolic group is residually finite. As a direct consequence, we obtain that the outer automorphism group of a limit group is residually finite.

11 pages, 1 figure. Section 3 is replaced by Theorem 1.3. More detailed arguments. Added new references. To appear in Journal of Pure and Applied Algebra