Abstract
In this article we study the geometry associated with the sub-elliptic operator
Acknowledgements
A part of this article is based on a lecture presented by the second author during the Spring School of EU Research and Training Network on “Geometric Analysis” which was held on March 1–6, 2004 at the Institute of Mathematics, Universität of Potsdam, Germany. The second author would like to thank the organizing committee, especially Professor B.-Wolfgang. Schulze for his warm hospitality during his visit to Germany. Partially supported by a William Fulbright Research grant and a competitive research grant at Georgetown University
Notes
Dedicated to Professor B.-Wolfgang Schulze on his sixtieth birthday