GJMS operators, Q-curvature, and obstruction tensor of partially   integrable CR manifolds
  We extend the notions of CR GJMS operators and Q-curvature to the case of partially integrable CR structures. The total integral of the CR Q-curvature turns out to be a global invariant of compact nondegenerate partially integrable CR manifolds equipped with an orientation of the bundle of contact forms, which is nontrivial in dimension at least five. It is shown that its variation is given by the curvature-type quantity called the CR obstruction tensor, which is introduced in the author's previous work. Moreover, we consider the linearized CR obstruction operator. Based on a scattering-theoretic characterization, we discuss its relation to the CR deformation complex of integrable CR manifolds. The same characterization is also used to determine the Heisenberg principal symbol of the linearized CR obstruction operator. 
Yoshihiko Matsumoto
math.DG math.CV