When are braid groups of manifolds Kähler?

Abstract

Sometime ago, we showed that a pure Artin braid group is not Kähler, i.e. it is not the fundamental group of a compact Kähler manifold. This used a result of Bressler, Ramachandran and the author that Kähler groups cannot be too "big". The goal here is to study the problem of Kählerness for other braid groups. The main result is that, with some trivial exceptions, the pure braid group of a Riemann surface with at least 2 strands is never Kähler. In some cases the proof uses the previous strategy, for others it plays off some homological properties of braid groups established beforehand against consequences of the Beauville-Catanese-Siu theorem. The braid group of a projective manifold of complex dimension 2 or more is shown to the fundamental group of a projective manifold, and hence Kähler.