Graph Polynomials for the Numbers of Independent Sets and Bipartite Cuts for Undirected Graphs

Abstract

The graph polynomial for the number of independent sets of size $k$ in a general undirected graph is shown to be equal to an elementary symmetric polynomial of the vertex monomials, which are determined by the edges incident at the vertices. The edge variables that comprise the vertex monomials are shown to be nilpotent of degree two. The index of nilpotency of the algebra generated by the graph's vertex monomials is the order of a maximum independent set of the graph. Graph polynomials for the number of cliques and vertex covers are derived from the graph polynomial for independent sets. The graph polynomial for the number of bipartite cuts is given as a coefficient of a multivariate Laurent polynomial.