Finitely presentable, non-Hopfian groups with Kazhdan's Property (T) and infinite outer automorphism group

Abstract

We give simple examples of Kazhdan groups with infinite outer automorphism groups. This answers a question of Paulin, independently answered by Ollivier and Wise by completely different methods. As arithmetic lattices in (non-semisimple) Lie groups, our examples are in addition finitely presented. We also use results of Abels about compact presentability of p-adic groups to exhibit a finitely presented non-Hopfian Kazhdan group. This answers a question of Ollivier and Wise.

9 pages, no figure. v4: statement of Theorem 3.1 corrected

References in corpus (1)

• Endomorphisms of relatively hyperbolic groups

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