Characterizing partition functions of the vertex model

Jan Draisma, Dion Gijswijt, László Lovász, Guus Regts, Alexander Schrijver

Published 2011-02-24Version 1

We characterize which graph parameters are partition functions of a vertex model over an algebraically closed field of characteristic 0 (in the sense of de la Harpe and Jones). We moreover characterize when the vertex model can be taken so that its moment matrix has finite rank.