Rank two cohomology jump loci on projective varieties

Abstract

Let $X$ be a smooth connected complex projective variety. We give a structure theorem for irreducible components of the reduced rank-two cohomology jump loci on $X$. More precisely, for such a component $Z$, if the general point of $Z$ is projectively virtually abelian or projectively rigid, then either $Z$ is a symmetric square of an algebraic torus, or a quotient of a torus by an involution, or its normalization $Z^ν$ is a torus. If the general point is neither, then either $Z^ν$ is a torus, or an étale quotient of $Q^ν \times T$ where $Q$ is a fixed-determinant, fixed-inertia component of the character variety of some DM-curve.