# Algebra/Topology seminar

Speaker: Marc Stephan (Bonn)

Title: Non-realizable equivariant chain complexes

Abstract: In 2017, Iyengar and Walker constructed equivariant chain complexes that are counterexamples to an algebraic version of Carlsson’s conjecture about free actions of elementary abelian p-groups G. To produce counterexamples to Carlsson’s conjecture, attempts have been made to realize these chain complexes topologically by free G- spaces. In this talk, I will explain that this is not possible, based on multiplicative properties of the spectral sequence obtained by filtration with powers of the augmentation ideal. This is joint work with Henrik Rüping.