VECTOR BUNDLES NEAR NEGATIVE CURVES: MODULI AND LOCAL EULER CHARACTERISTIC

We study moduli of vector bundles on a two-dimensional neighbourhood Z(k) of an irreducible curve l congruent to IP1 with l(2) = -k and give an explicit construction of their moduli stacks. For the case of instanton bundles, we stratify the stacks and construct moduli spaces. We give sharp bounds for the local holomorphic Euler characteristic of bundles on Zk and prove existence of families of bundles with prescribed numerical invariants. Our numerical calculations are performed using a Macaulay 2 algorithm, which is available for download at http://www.maths.ed.ac.uk/similar to s0571100/Instanton/.