A Most General Edge Elimination Graph Polynomial

We look for graph polynomials which satisfy recurrence relations on three kinds of edge elimination: edge deletion, edge contraction and deletion of edges together with their end points. Like in the case of deletion and contraction only (W. Tutte, 1954), it turns out that there is a most general polynomial satisfying such recurrence relations, which we call ξ(G, x, y, z). We show that the new polynomial simultaneously generalizes the Tutte polynomial, the matching polynomial, and the recent generalization of the chromatic polynomial proposed by K.Dohmen, A.Pönitz and P.Tittman (2003), including also the independent set polynomial of I. Gutman and F. Harary, (1983) and the vertex-cover polynomial of F,M. Dong, M.D. Hendy, K.T. Teo and C.H.C. Little (2002). We establish two definitions of the new polynomial: first, the most general confluent recursive definition, and then an explicit one, using a set expansion formula, and prove their identity. We further expand this result to edgelabeled graphs as was done for the Tutte polynomial by T. Zaslavsky (1992) and B. Bollobás and O. Riordan (1999). The edge labeled polynomial ξlab(G, x, y, z, t̄) also generalizes the chain polynomial of R.C. Read and E.G. Whitehead Jr. (1999). Finally, we discuss the complexity of computing ξ(G, x, y, z). Partially supported by a grant of the Graduate School of the Technion–Israel Institute of Technology Partially supported by a grant of the Graduate School of the Technion–Israel Institute of Technology Partially supported by a grant of the Fund for Promotion of Research of the Technion– Israel Institute of Technology and a grant of the Israel Science Foundation (2007-2010)