Just before the opening of the conference, a small symposium was arranged for the junior participants, at which the following survey lectures were delivered: "The Energy-Momentum Tensor", by Dr. N.V. Mitskevich (Samarkand); "Cosmological Models", by Dr. A.L. Zel'manov (GAISh and MGU); and "Relativistic Hydrodynamics", by Prof. K. P. Stanyukovich (MVTU). During the conference itself, Prof. Ya. A. Smorodinskii (OIYal, Dubna) gave a lecture entitled "Neutrino Physics".
The conference sessions were well attended (usually 150 to 200 people were present), and lively debates constantly took place, developing at times into heated discussions.
The conference opened with an introductory address by the representa tive of the organizing committee, Prof. D. D. Ivanenko, who reviewed in brief the aims of the conference. The conference then proceeded to its first topic of discussion, "The Classical Theory of Gravitation".
The first report was read by Prof. A. Z. Petrov (Kazan University), who gave an account of his fundamental studies of gravitation theory (one of the main contributions to this field during the last decade). A detailed account of these studies cannot be given here; we should mention, however, that Petrov has classified the solutions of Einstein's equations according to three mutually irreducible types. It was shown that practically all the solutions known at that time could be reduced to the first type, and that the requirement of a flat space at infinity applies only to this type (this requirement being intrinsically invalid for the other two types). Petrov's
studies stimulated considerably the search for new solutions, and now solutions of all three types have been obtained.
New solutions of Einstein's equations were analyzed and discussed in the contributions of N. V. Mitskevich (Samarkand), A. A. Koppel' (Tartu), V. S. Brezhnev (MGU), and Prof. N. M. Petrova (Alma-Ata).
The Schwarzschild solution is known to have a singularity at certain values of the gravitational radius. The physical interpretation of this problem was dealt with in the reports of the young theoreticians V. A. Unt (Tartu), I. D. Novikov (MGU), and Yu. A. Rylov (MGU).
Some interesting studies of particle motion near the gravitational radius were discussed by S. L. Galkin (MGU). These investigations are of particular interest in connection with the prediction recently made by V. A. Ambartsumyan and G. S. Saakyan concerning the existence of hyperon stars (stars consisting mainly of superheavy hyperons) having radii comparable to the gravitational radius.
The second session on the first day of the conference was combined with a session of the Sixth All-Union Conference on Extragalactic Nebulae, which was being held concurrently. Reports were read by E. M. Lifshits, V. V. Sudakov, and I. M. Khalatnikov (Institute for Physical Problems,