Volume 18, issue 2 (2018)

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ISSN (electronic): 1472-2739
ISSN (print): 1472-2747
Outer actions of $\mathrm{Out}(F_n)$ on small right-angled Artin groups

Dawid Kielak

Algebraic & Geometric Topology 18 (2018) 1041–1065
Abstract

We determine the precise conditions under which SOut(Fn), the unique index-two subgroup of Out(Fn), can act nontrivially via outer automorphisms on a RAAG whose defining graph has fewer than 1 2 n 2 vertices.

We also show that the outer automorphism group of a RAAG cannot act faithfully via outer automorphisms on a RAAG with a strictly smaller (in number of vertices) defining graph.

Along the way we determine the minimal dimensions of nontrivial linear representations of congruence quotients of the integral special linear groups over algebraically closed fields of characteristic zero, and provide a new lower bound on the cardinality of a set on which SOut(Fn) can act nontrivially.

Keywords
Out(F_n), RAAGs
Mathematical Subject Classification 2010
Primary: 20F65
Secondary: 20F28, 20F36
References
Publication
Received: 25 February 2017
Revised: 14 August 2017
Accepted: 21 November 2017
Published: 12 March 2018
Authors
Dawid Kielak
Fakultät für Mathematik
Universität Bielefeld
Bielefeld
Germany