Finding involutions with small support

Abstract

We show that the proportion of permutations $g$ in $S_n$ or $A_n$ such that $g$ has even order and $g^{|g|/2}$ is an involution with support of cardinality at most $\lceil n^{\epsilon }\rceil$ is at least a constant multiple of $\epsilon$. Using this result, we obtain the same conclusion for elements in a classical group of natural dimension $n$ in odd characteristic that have even order and power up to an involution with $(-1)$-eigenspace of dimension at most $\lceil n^{\epsilon }\rceil$ for a linear or unitary group, or $2\lceil \lfloor n/2{\rfloor }^{\epsilon }\rceil$ for a symplectic or orthogonal group.

References in corpus (1)

• Fast recognition of alternating groups of unknown degree