[en] The evolution of ideas on the nature of the Vavilov-Cherenkov radiation is discussed. The period between Vavilov's ideas, advanced in 1934, and the formulation of a quantitative theory of the phenomenon in 1937 is surveyed

[en] A peculiar situation which has persisted for a quarter of a century in the theory of the multiple production of high-energy hadrons is reviewed. On the one hand, cosmic-ray work established the concept of heavy intermediate formation: fireballs: a long time ago. The evolution and decay of these fireballs can be described thermodynamically (in particular, hydrodynamically). On the other hand, the advent of ultrarelativistic proton accelerators stimulated Feynman-diagram, peripheral, and Regge approaches to the description of few-particle events; later, multiperipheral, parton (''parton comb''), etc., approaches were taken to describe many-particle events. Over the past decade, the failure of Feynman scaling in the pionization region, the observation of clustering, etc., and the success of the thermodynamic interpretation of accelerator experiments, which has won new support from quantum chromodynamics, have marked a substantial convergence of the models which previously appeared mutually exclusive. A suitable approximate model describing this convergence is a model which has been under development for a long time now, peripheral or even multiperipheral in its essence but including thermodynamic subsystems. This convergence now seems even more pronounced than was thought only recently; the characteristics of thermodynamic entities are manifested time and time again in accelerator experiments. At the same time, for processes involving only a few particles (which thermodynamics cannot claim to describe), the picture is still dominated by both the phenomenological interpretation, based on reggeon exchange, and the quantum chromodynamics of point quarks for deep inelastic reactions involving the transfer of a large 4-momentum (the same is true for reactions involving the fragmentation of the incident particle or of the target)

[en] A review of experimental and theoretical studies of radiative lifetimes of excited states of the hydrogen atom, of atoms of alkali metals, and atoms of the copper subgroup is presented. A complete compilation of all published values of radiative lifetimes of all excited states with a critical analysis for every atom is given. The regularities in the variation of radiative lifetimes in spectral series of excited states are brought out and constants of the power-law dependences on the effective principal quantum number are determined. A correlation between the behavior of lifetimes and the effective orbital parameter is established and it is proposed to use this correlation for the determination of the application limits of the power-law constants for evaluation of lifetimes of uninvestigated states. On the basis of a critical analysis of published sources, of the regularities in the variation of lifetimes and of a statistical treatment of values available in the literature, a table of recommended values of radiative lifetimes of excited states of all atoms of the first group is compiled

[en] A translation presented of the article announcing the identification of ω bosons at the CERN pp-bar collider

[en] The current state of research on the free oscillations of the sun is reviewed. Observational data on oscillations with periods from 5 to 160 min published through the end of 1980 are described. The interpretation of these data in connection with research on the internal structure of the sun is discussed. A theory of the free oscillations in the linear adiabatic approximation is described; differential rotation is taken into account. The principles for classifying the theoretical normal modes are discussed. The problem of the excitation of the solar oscillations is outlined. The theoretical normal-mode spectra of Jupiter and Saturn are discussed

[en] An attempt is made to present an instanton ''calculus'' in a relatively simple form. The physical meaning of instantons is explained by the example of the quantum-mechanical problem of energy levels in a two-humped potential. The nonstandard solution to this problem based on instantons is analyzed, and the reader is acquainted with the main technical elements used in this approach. Instantons in quantum chromodynamics are then considered. The Euclidean formulation of the theory is described. Classical solutions of the field equations (the Belavin-Polyakov-Shvarts-Tyupkin instantons) are obtained explicitly and their properties are studied. The calculation of the instanton density is described and the complete result is given for an arbitrary number of colors. The effects associated with fermion fields are briefly described

[en] The review is devoted to a discussion of the definition and properties of energy in Einstein's theory of gravitation. Asymptotically flat space-time is defined in terms of admissible asymptotically Cartesian coordinates and a corresponding group of coordinate transformations. A Lagrange function is introduced on such a space-time, and a generalized Hamiltonian formulation of the theory of gravitation is constructed in accordance with Dirac's method. The energy is defined as the generator of displacement with respect to the asymptotic time. It is shown that the total energy of the gravitational field and the matter fields with normal energy-momentum tensor is positive and vanishes only in the absence of matter fields and gravitational waves. The proof follows Witten's proof but contains a number of corrections and improvements. Various standard criticisms of the energy concept in general relativity are discussed and shown to be without substance

[en] This review, occasioned by the fiftieth anniversary of the discovery of the neutron, considers the most important papers on fundamental studies of the properties of the neutron. Some of the researches are briefly expounded, and the present values of the fundamental quantities that characterize the neutron as an elementary particle are given

[en] The review treats the problem of radiation of relativistic charged particles in matter. The radiation of fast particles in an external field is considered from a unified point of view for an amorphous medium and for a single crystal. The basic attention is paid to the process of radiation in a single crystal where an enhancement of the radiation occurs as compared with an amorphous medium. This effect is shown to be due to the coherent and the interference mechanisms of radiation of relativistic particles in single crystals. First we outline the Born theory (quantum and classical) of coherent radiation of fast particles and show that this theory is valid if the particle propagates through the crystal far from the directions of channeling and if the scattering angle of the particle is small compared with the typical radiation angle of a relativistic particle. Then we show that a violation of these conditions leads to new effects in radiation such as, e.g., the effect of intense radiation of superbarrier and channeled particles, and the effect of suppression of coherent radiation. The comparison of theoretical and experimental results confirms the existence of new effects in the radiation. In conclusion, we review briefly new physical effects that must take place in single crystals at high energies in several other electrodynamical processes

[en] The theory for electron detachment in low-energy collisions of negative ions and atoms and experimental methods for studying this detachment are reviewed. Theory and experiment are compared, particularly with regard to the energy spectra of the emitted electrons. The relationship between electron detachment and nonequilibrium processes in plasmas is discussed, as is the relationship between detachment and the occupation of highly excited states of the colliding particles. The typical parameters of the process, the possibility of extracting them from theory and experiment, and the various theoretical methods and models for detachment and ionization are all discussed. The excitation and decay of approximately stationary states (autoionization and autodetachment states) of quasimolecules and also of isolated atoms and negative ions are discussed. Isotopic effects and the corresponding theory are discussed. Information on the behavior of unstable terms of the colliding atomic particles and of the widths of these terms cannot be obtained by other methods, so that this branch of the physics of atomic collisions may be singled out for separate discussion as the ''electron spectroscopy of unstable quasimolecular states.''