Ruelle, David

Graph-Counting Polynomials for Oriented Graphs

If F is a set of subgraphs F of a finite graph E we define a graph-counting polynomial p{sub F}(z)=∑{sub F∈F}z{sup |F|} In the present note we consider oriented graphs and discuss some cases where F consists of unbranched subgraphs E. We find several situations where something can be said about the location of the zeros of p{sub F}.