Perverse sheaves on varieties with large fundamental groups

Abstract

We conjecture that any perverse sheaf on a compact aspherical Kähler manifold has non-negative Euler characteristic. This extends the Singer-Hopf conjecture in the Kähler setting. We verify the stronger conjecture when the manifold X has non-positive holomorphic bisectional curvature. We also show that the conjecture holds when X is projective and in possession of a faithful semi-simple rigid local system. The first result is proved by expressing the Euler characteristic as an intersection number involving the characteristic cycle, and then using the curvature conditions to deduce non-negativity. For the second result, we have that the local system underlies a complex variation of Hodge structure. We then deduce the desired inequality from the curvature properties of the image of the period map.