Vanishing of Algebraic Brauer-Manin Obstructions

Let X be a homogeneous space of a quasi-trivial k-group G, with geometric stabilizer ̅H, over a number field k. We prove that under certain conditions on the character group of ̅H, certain algebraic Brauer-Manin obstructions to the Hasse principle and weak approximation vanish, because the abelian groups where they take values vanish. When ̅H is connected or abelian, these algebraic Brauer-Manin obstructions to the Hasse principle and weak approximation are the only ones, so we prove the Hasse principle and weak approximation for X under certain conditions. As an application, we obtain new sufficient conditions for the Hasse principle and weak approximation for linear algebraic groups.