Author Description

The Surveys in Differential Geometry are supplements to the Journal of Differential Geometry, which are published by International Press. They include significant invited papers combining original research and overviews of the most current research in specific areas of interest to the growing Journal of Differential Geometry community. The survey volumes serve as continuing references, inspirations for new research, and introductions to the variety of topics of interest to differential geometers. These supplements are published annually since 1999. In 1993, the Journal of Differential Geometry sponsored the second conference on Differential Geometry. While the first conference was held in 1990, there is still significant interest in the proceedings (published in 1991) of Surveys in Differential Geometry 1991, and there continues to be developments in the subject. For this reason, we intend to continue sponsoring this conference and the accompanying publication once every three years. The conference was held at Harvard University, coinciding with the celebration of Raoul Bott's 70th birthday. We are very grateful to all the speakers, who attracted a large audience, and to the three hundred participants, whose participation made this conference a big success. This volume (Vol.2) of Surveys in Differential Geometry is based on the lectures given during the 2nd conference of Journal of Differential Geometry.