Distinguishing Chromatic Numbers of Wreath Products

C.J. Hodgins1, K. Seyffarth2
1Continuing Academic Learner Services Southern Alberta Institute of Technology Calgary, AB, T2M 0L4, Canada
2Department of Mathematics and Statistics University of Calgary Calgary, AB, T2N 1N4, Canada

Abstract

The distinguishing chromatic number of a graph \( G \) is the least integer, \( \chi_D(G) \), for which \( G \) has a coloring of its vertices so that adjacent vertices receive different colors, and the identity is the only automorphism of \( G \) that preserves vertex colors. Our focus is on determining the distinguishing chromatic numbers of wreath products of graphs, extending the work of Tang. We prove that if \( C_n \) is a cycle with \( n \) vertices and \( P_n \) is a path with \( n \) vertices, then \( \chi_D(C_n[G]) \) and \( \chi_D(P_n[G]) \) can be found for any connected graph \( G \). We also obtain an upper bound on \( \chi_D(T[G]) \) when \( T \) is a tree and \( G \) is any connected graph. Some of our results depend on the notion of inequivalent colorings. Cheng introduces inequivalent colorings and provides a formula for computing the number of inequivalent distinguishing \( k \)-colorings of a rooted tree. We add to this work by obtaining an expression for computing the number of inequivalent distinguishing \( k \)-colorings of a cycle.