Abstract
We consider a compact pseudo-hermitian manifold (M,\theta, J), that is a manifold equipped with a contact form \theta and CR structure J. We consider a conformal deformation of the contact form to obtain a complete, singular contact form and a corresponding Yamabe problem. We estimate then the Hausdorff dimension of the singular set. The conformal geometry analog of this result is due to R. Schoen and S. -T. Yau. These results go back to Huber for Riemann surfaces. In the second part of our paper we investigate the CR developing map for three dimensional CR manifolds. We establish the injectivity of the developing map essentially using the same strategy as Schoen and Yau for the conformal case which is based on the positive mass theorem. Higher dimensional analogs of Huber's theorem in the conformal case for Q curvature are due to Alice Chang, Jie Qing and P. Yang. The paper will appear in a special volume in memory of Haim Brezis in Communications in Contemporary Math.