Prime-to-p étale covers of algebraic groups

Michel Brion, Tamás Szamuely

Published 2011-09-13, updated 2012-09-28Version 4

Let G be a connected algebraic group over an algebraically closed field of characteristic p (possibly 0), and X a variety on which G acts transitively with connected stabilizers. We show that any \'etale Galois cover of X of degree prime to p is also homogeneous, and that the maximal prime-to-p quotient of the \'etale fundamental group of X is commutative. We moreover obtain an explicit bound for the number of topological generators of the said quotient. When G is commutative, we also obtain a description of the prime-to-p torsion in the Brauer group of G.