The past decade has witnessed cosmology undergoing a rapid transition. A field which earlier had wide room for theoretical speculations, is finding itself tightly constrained by observations which now put severe restrictions on the theoretical models and even rule out some of them. All ongoing and future theoretical efforts have to take into account this rapidly emerging observational evidence. This interplay between theory and observations has been the main theme of this workshop.

The workshop brought together people working in a large variety of fields ranging from observational astronomy to theoretical high energy physics and we witnessed very intense exchange of ideas amongst the participants both during the workshop talks and during informal sessions which usually continued very late into the night invariably delaying the start of the next days schedule. This volume records the proceedings of a part of the workshop which consisted of a set of review talks one hour in duration and more specialized talks half an hour in duration. Unfortunately we are unable to present any record of the proceedings of an equally important part of the workshop which was carried out through informal discussions amongst the participants.

We hope that the proceedings of this workshop will provide very useful reference material for people working in this field in India.

The workshop was funded by the Department of Science and Technology, Indian National Science Academy and Indian Institute of Technology, Kharagpur.

This workshop would not have been possible without the active support of our colleagues who braved the uncertainties of travel in India to reach a little known place called Kharagpur to attend this workshop. We also wish to thank Prof. Amitabha Ghosh, Director, IIT, Kharagpur for his help and encouragement at every stage of planning and organizing the workshop. We are very grateful to Ajit Srivastava who helped us edit the part of the proceedings dealing with topological defects. We would also like to put on record our gratitude to Gopal Lingam for his help and to Akhilesh Singh for his invaluable assistance in organizing and running the workshop and in editing the proceedings. Finally we wish to thank all the students volunteers, our colleagues in the Physics Department, the IIT administration and the Technology Guest House for their valuable support which made this workshop a success.

13 October 1999