Distance magic labelings of Cartesian products of cycles

Abstract: A graph of order $n$ is distance magic if it admits a bijective labeling of its vertices with integers from $1$ to $n$ such that each vertex has the same sum of the labels of its neighbors. In this paper we classify all distance magic Cartesian products of two cycles, thereby correcting an error in a widely cited paper from 2004. Additionally, we show that each distance magic labeling of a Cartesian product of cycles is determined by a pair or quadruple of suitable sequences, thus obtaining a complete characterization of all distance magic labelings of these graphs. We also determine a lower bound on the number of all distance magic labelings of $C_{m} \square C_{2m}$ with $m \ge 3$ odd.