# CR geometry in 3-D

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## Abstract

CR geometry studies the boundary of pseudo-convex manifolds. By concentrating on a choice of a contact form, the local geometry bears strong resemblence to conformal geometry. This paper deals with the role conformally invariant operators such as the Paneitz operator plays in the CR geometry in dimension three. While the sign of this operator is important in the embedding problem, the kernel of this operator is also closely connected with the stability of CR structures. The positivity of the CR-mass under the natural sign conditions of the Paneitz operator and the CR Yamabe operator is discussed. The CR positive mass theorem has a consequence for the existence of minimizer of the CR Yamabe problem. The pseudo-Einstein condition studied by Lee has a natural analogue in this dimension, and it is closely connected with the pluriharmonic functions. The author discusses the introduction of new conformally covariant operator *P*-prime and its associated *Q*-prime curvature and gives another natural way to find a canonical contact form among the class of pseudo-Einstein contact forms. Finally, an isoperimetric constant determined by the *Q*-prime curvature integral is discussed.

## Keywords

Paneitz operator Embedding problem Yamabe equation Mass*P*-prime

*Q*-prime curvature

## 2000 MR Subject Classification

58J05 53C21## Preview

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## Notes

### Acknowledgments

The author takes this opportunity to thank his collaborators who provide inspiration and support in these investigations: Jeffrey Case, Sagun Chanillo, Jih-Hisn Cheng, Hung-Lin Chiu, Rod Gover, Chin-Yu Hsiao, Andrea Malchiodi, Yi Wang and Polam Yung.

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