On the behavior of stringy motives under Galois quasi-étale covers

Abstract

We investigate the behavior of stringy motives under Galois quasi-étale covers. We prove that they descend under such covers in a sense defined via their Poincaré realizations. Further, we show that such descent is strict in the presence of ramification. As a corollary, we reduce the problem regarding the finiteness of the étale fundamental group of KLT singularities to a DCC property for their stringy motives. We verify such DCC property for surfaces in arbitrary characteristic. As an application, we give a characteristic-free proof for the finiteness of the étale fundamental group of log terminal surface singularities, which was unknown in equal characteristics 2 and 3 and in mixed characteristics.

38 pages, 6 figures, comments are very much welcome, final version accepted for publication in Documenta Mathematica