Isotopy graphs of Latin tableaux

Abstract

Latin tableaux are a generalization of Latin squares, which first appeared in the early 2000's in a paper of Chow, Fan, Goemans, and Vondrák. Here, we extend the notion of isotopy, a permutation group action, from Latin squares to Latin tableaux. We define isotopy graphs for Latin tableaux, which encode the structure of orbits under the isotopy action, and investigate the relationship between the shape of a Latin tableau and the structure of its isotopy graph. Our main result shows that for any positive integer d, there is a Latin tableau whose isotopy graph is a d-dimensional cube. We show that most isotopy graphs are triangle-free, and we give a characterization of all the Latin tableaux for which the isotopy graph contains a triangle. We also establish that each connected component of an isotopy graph is regular, and give a formula for the degree of each vertex in a connected component of an isotopy graph which depends on both the shape of the tableau and the filling.