Twisted Hodge groups and deformation theory of Hilbert schemes of points on surfaces via Hodge modules

Abstract: Given a smooth compact complex surface together with a holomorphic line bundle on it, using the theory of Hodge modules, we compute the twisted Hodge groups/numbers of Hilbert schemes (or Douady spaces) of points on the surface with values in the naturally associated line bundle. This proves an amended version of Boissi`ere's conjecture proposed by the author in his joint work with Belmans and Krug, and extends G\"ottsche--Soergel's formula for Hodge numbers and G\"ottsche's formula for refined $\chi_y$-genera to any compact complex surface, without K\"ahlerness assumption. As an application, we determine the tangent space and the obstruction space of the formal deformation theory of Douady spaces of compact complex surfaces. Analogous results are obtained for nested Hilbert schemes.