Groups acting purely loxodromically on products of hyperbolic graphs

Abstract

We consider the class of countable groups possessing an action on a finite product of hyperbolic graphs where every infinite order element acts loxodromically. When the graphs are locally finite, we obtain strong structure theorems for the groups in this subclass, so that mapping class groups of genus at least 3 (and $Aut(F_n)$ and $Out(F_n)$ for $n\geq 4$) are not in this subclass. This contrasts with the general case, where Bestvina, Bromberg and Fujiwara showed the existence of proper actions of mapping class groups on a finite product of quasitrees. In particular these quasitrees cannot be locally finite.