Chromatic Polynomials and the Symmetric Group

In this paper we give first a new combinatorial interpretation of the coefficients of chromatic polynomials of graphs in terms of subsets of permutations. Motivated by this new interpretation, we introduce next a combinatorially defined polynomial associated to a directed graph, and prove that it is related to chromatic polynomials. These polynomials are a specialization of cover polynomials of digraphs.I am grateful to the Swiss National Science Foundation for its partial financial supportFinal version received: June 25, 2003