Cycle structure of autotopisms of quasigroups and Latin squares

Abstract

An autotopism of a Latin square is a triple $(\alpha,\beta,\gamma)$ of permutations such that the Latin square is mapped to itself by permuting its rows by $\alpha$, columns by $\beta$, and symbols by $\gamma$. Let $\mathrm{Atp}(n)$ be the set of all autotopisms of Latin squares of order $n$. Whether a triple $(\alpha,\beta,\gamma)$ of permutations belongs to $\mathrm{Atp}(n)$ depends only on the cycle structures of $\alpha$, $\beta$ and $\gamma$. We establish a number of necessary conditions for $(\alpha,\beta,\gamma)$ to be in $\mathrm{Atp}(n)$, and use them to determine $\mathrm{Atp}(n)$ for $n\le17$. For general $n$ we determine if $(\alpha,\alpha,\alpha)\in\mathrm{Atp}(n)$ (that is, if $\alpha$ is an automorphism of some quasigroup of order $n$), provided that either $\alpha$ has at most three cycles other than fixed points or that the non-fixed points of $\alpha$ are in cycles of the same length.