The cone of Betti diagrams of bigraded artinian modules of codimension two
arXiv:1001.3238 · doi:10.1007/978-3-642-19492-4
Abstract
We describe the positive cone generated by bigraded Betti diagrams of artinian modules of codimension two, whose resolutions become pure of a given type when taking total degrees. If the differences of these total degrees, p and q, are relatively prime, the extremal rays are parametrised by order ideals in N^2 contained in the region px + qy < (p-1)(q-1). We also consider some examples concerning artinian modules of codimension three.
15 pages