On the unramified cohomology of certain quotient varieties

Abstract

In this note, we consider unramified cohomology with $\mathbb{Z}/2$ coefficients for some (degree two) quotient varieties and describe a method that allows one to prove the non-vanishing of these groups under certain conditions. We apply this method to prove a non-vanishing statement in the case of Kummer varieties. Combining this with work of Colliot-Thélène and Voisin, we obtain a new type of three-dimensional counterexample to the integral Hodge conjecture.

Same as first version; a revised version of another paper was mistakenly submitted as version 2 along with the journal reference. Thanks to Stefan Schreieder for catching this