Ivan Martino: Subspace arrangements and motives of classifying stacks of reflection groups

In this talk I plan to prove that the motivic class of the classifying stack of every finite linear (or projective) reflection group is trivial in the Grothendieck ring of algebraic stacks.

The proof rests on a combinatorial analysis of a formula by T. Ekedahl that we interpret in terms of certain subspace arrangements associated to any representation of a finite group.