INTRODUCTION
The Marcel Grossmann meetings have been conceived with the aim of reviewing recent advances in gravitation and general relativity with major emphasis on their mathematical foundations and physical predictions. Their main object is to elicit contributions which deepen our understanding of space-time structures as well as review the status ot experiments verifying Einstein's Theory of Gravitation. These two volumes are the record of the fourth meeting.
The contributions include: Bar Gravitational Wave Detectors, Black Holes, Classical Relativity, Computer Relativity, Cosmology & Inos, Early Cosmology, Exact Solutions, Gauge Theories, Gravitationally Collapsed Objects, Gravitational Wave Detectors, History of General Relativity, Interferometers for Gravitational Waves, Kaluza Klein Theories, Quantum Gravity, Lagrangian Theories, Microwave Background, Precision Gravitational Measurements, Relativistic Effects in Astrophysics, Relativistic Self-Gravitating Systems, Space Station Observations and Experiments, Supergravity.
I would like to thank the people who made this fourth meeting possible as well as the speakers and participants who came from all over the world.
The participants of this meeting had the special opportunity of having an audience in the Vatican with His Holiness Pope John Paul II, who gave an address on the human and social values of scientific research. This address has been reproduced as the first contribution to these proceedings. For that special occasion two artists dedicated unique expressions of their own work to the Grossmann meeting. The first, Attilio Pierelli, presented a silver sculpture of the symbol of the Grossmann meetings (T.E.S.T.:
Trascinamento di Eventi Spazio Temporali or "Dragging of Spacetime Events") dedicated to the Pope. Copies of this sculpture were awarded to three participants of the fourth meeting for their special scientific contributions: William Fairbank, for his work in gravitation and low temperature techniques; Riccardo Giacconi, for his work on space astrophysics; and Abdus Salam, for his work on unifying fundamental interactions. The second artist, Federico Amendola, inspired by the audio version of the electromagnetic signals of the Vela Pulsar (0833-45), created an original electronic musical composition built on the Pulsar signals themselves as a "natural instrument". Cetra Art Recording and Cherubini are thanked for their technical contributions to the executions and taping of the Amendola composition. These artistic activities were coordinated by Anna Imponente of the Museum of Modern Art in Rome.
The success of the meeting was enhanced by the effectiveness of the chairmen of the sessions, who maintained an excellent equilibrium between the presentations, interventions and general discussion and, with the benefit of their scientific knowledge, gave due perspective to important new contributions.
My deep gratitude goes to the members of the International Organizing
Committee: S. Chandrasekhar, Yvonne Choquet-Bruhat, Juergen Ehlers, Fang Li Zhi, Yuval Ne'eman, Abdus Salam, Humitaka Sato, Steven Weinberg and Jacov B. Zel'dovich,'and of the Local Organizing Committee: A. Cavaliere, T. Damour, M. Demianski, G. Denardo, F. Everitt, A. Figa' Talamanca, R. Jantzen, F. Melchiorri, G. Pizzella and W. Stoeger and to all of the organizations who made this meeting possible with their generous help.
I would like to thank, for their invaluable collaboration, Bryan Boynton, Lucio di Donato, Elisabetta di Silvestro, Prudence Egerton, Giuliana Marchetti, and the students in the Physics Department at the University of Rome who helped generously during the entire meeting: Lorella Angelini, Massimo Bianchi, Paolo Carini, Gregono D'Agostino, Marco de Pretis, Corrado di Natale, Basiho Esposito, Adriano Fontana, Fabrizio Forzano, Edmondo Giovannozzi, Dario Grasso, Valeria Lo Schiavo, Maria Marsella, Alessandro Massarotti, Roberto Onofrio, Alberto Ranucci, Giada Rauti and Ersilia Vaudo.
Finally, I would like to express my warmest thanks to Marek Demianski for his substantial assistance both in the preparations for and throughout the meeting, and for his constant help in editing the manuscripts, and to Gerda Wolzak, her help has been invaluable in coordinating the editorial procedures and the many organizational aspects of this Fourth Marcel Grossmann Meeting.