Toric ideals of normalized graph algebras

A graph-theoretic method, simpler than existing ones, is used to characterize the minimal set of monomial generators for the integral closure of any algebra of polynomials generated by quadratic monomials. The toric ideal of relations between these generators is generated by a set of binomials, defined graphically. The spectra of the original algebra and of its integral closure turn out to be canonically homeomorphic.Comment: 9 pages, no figures. v2: major rewrite. v3: minor improvements. v4: new title, old reference located, other small change