Georgia Institute of Technology College of Sciences

We study various binomial and monomial ideals related to the theory of divisors, orientations, and matroids on graphs. We use ideas from potential theory on graphs and from the theory of Delaunay decompositions for lattices to describe minimal polyhedral cellular free resolutions for these ideals. We will show that the resolutions of all these ideals are closely related and that their Betti tables coincide. As corollaries we give conceptual proofs of conjectures and questions posed by Postnikov and Shapiro, by Manjunath and Sturmfels, and by Perkinson, Perlman, and Wilmes. Various other results related in the theory of chip-firing games on graphs -- including Merino's proof of Biggs' conjecture and Baker-Shokrieh's characterization of reduced divisors in terms of potential theory -- also follow immediately from our general techniques and results.