Brauer groups and quotient stacks

Abstract. A natural question is to determine which algebraic stacks are quotient stacks. In this paper we give some partial answers and relate it to the question of whether, for a scheme X, the natural map from the Brauer group (equivalence classes of Azumaya algebras) to the cohomological Brauer group (the torsion subgroup of H2(X, G m)) is surjective. 1. Introduction. Quotient