Abstract
We provide a criterion for non-vanishing of period integrals on automorphic representations of a general linear group over a division algebra. We consider three different periods: linear periods, twisted-linear periods and Galois periods. Our criterion is a local-global principle, which is stated in terms of local distinction, a further local obstruction, and poles of certain global $L$-functions associated to the underlying involution via the Jacquet-Langlands correspondence. Our local-global principle follows from a careful analysis of singularities of local and global intertwing periods. Our results generalize to inner forms, known results for general linear groups. In particular, we complete the proof of one direction of the Guo-Jacquet conjecture.