Fixed point conditions for non-coprime actions

Abstract:

In the setting of finite groups, suppose $J$ acts on $N$ via automorphisms so that the induced semidirect product $Nrtimes J$ acts on some non-empty set $Omega$ , with $N$ acting transitively. Glauberman proved that if the orders of $J$ and $N$ are coprime, then $J$ fixes a point in $Omega$ . We consider the non-coprime case and show that if $N$ is abelian and a Sylow $p$ -subgroup of $J$ fixes a point in $Omega$ for each prime $p$ , then $J$ fixes a point in $Omega$ . We also show that if $N$ is nilpotent, $Nrtimes J$ is supersoluble, and a Sylow $p$ -subgroup of $J$ fixes a point in $Omega$ for each prime $p$ , then $J$ fixes a point in $Omega$ .