On the failure of the integral Hodge/Tate conjecture for products with projective hypersurfaces

Abstract

In this paper we show the failure of the integral Hodge/Tate conjecture for the product of an Enriques surface with a smooth odd-dimensional projective hypersurface. To do this, we use a specialization argument of Colliot-Th\'el\`ene applied to Schreieder's refined unramified cohomology. The results obtained in this way give an interpretation of Shen's result in terms of refined unramified cohomology. Moreover, using this interpretation, we avoid the need to work over the complex numbers so that we may conclude that Shen's result also holds over general algebraically closed fields of characteristic not 2.