A note on finite groups with an automorphism inverting or squaring a non-negligible fraction of elements

Abstract

We show that for a finite group $G$, the commuting probability of $G$ can be explicitly bounded from below in a nontrivial way by a function in the maximum fraction of elements inverted resp. squared by an automorphism of $G$. Using these bounds together with a result of Guralnick and Robinson gives upper bounds on the index of the Fitting subgroup of $G$ under each of the two conditions that $G$ have an automorphism inverting resp. squaring at least $\rho|G|$ many elements in $G$, for $\rho\in\left(0,1\right]$ fixed. This is an improvement on previous results of the author.