Hunting Vector Bundles on $\mathbb{P}^1 \times \mathbb{P}^1$

Abstract

Boij-Söderberg theory concerns resolutions of graded modules over a polynomial ring over a field. Specifically Boij-Söderberg theory gives a description of the cone of Betti diagrams for Cohen-Macaulay modules. Eisenbud and Schreyer discovered a duality between the cone of Betti diagrams and the cone of cohomology tables for vector bundles on projective space. In the dual theory an important role is played by so called natural vector bundles $E$ which have the property that the cohomology of every twist of $E$ is concentrated in a single degree. In [4], Eisenbud and Schreyer consider the bi-graded theory on $\mathbb{P}^1 \times \mathbb{P}^1$ and conjecture that natural vector bundles exist with prescribed Euler characteristic. The Euler characterist depends on three rational number $α,β, γ$. We prove this conjecture provided that $α,β$ are not both integral.