Instituto de Matemática, Universidade Federal da Bahia, Av. Ademar de Barros, s/n, 40170-210 Salvador, BA, Brazil
Abstract:
We consider the jacobian module of a set of squarefree monomials of degree corresponding to the edges of a connected bipartite graph . We show that for such a graph the number of its primitive cycles (i.e., cycles whose chords are not edges of ) is the second Betti number in a minimal resolution of the corresponding jacobian module. A byproduct is a graph theoretic criterion for the subalgebra to be a complete intersection.