Even and odd instanton bundles on Fano threefolds of Picard number one

Abstract

We consider an analogue of the notion of instanton bundle on the projective 3-space, consisting of a class of rank-2 vector bundles defined on smooth Fano threefolds X of Picard number one, having even or odd determinant according to the parity of K X . We first construct a well-behaved irreducible component of their moduli spaces. Then, when the intermediate Jacobian of X is trivial, we look at the associated monads, hyperdeterminants and nets of quadrics. We also study one case where the intermediate Jacobian of X is non-trivial, namely when X is the intersection of two quadrics in $${\mathbb{P}^5}$$ , relating instanton bundles on X to vector bundles of higher rank on a the curve of genus 2 naturally associated with X.