Table of contents

This paper reviews the present status of the physics of bottomonium: a bound system consisting of a heavy b quark and the antiquark . The basic experimental data on the levels of bottomonium are presented. Theoretical methods for describing the properties of these levels are discussed. Questions pertaining to the spectroscopy of bottomonium, including the fine and hyperfine splittings, radiative transitions between levels, and annihilation decays of the b system, are discussed. Effects which are not describable by quantum-chromodynamics perturbation theory are taken into account. Transitions between bottomonium levels involving the emission of light muons are discussed. The possibilities of a search for hypothetical new particles and effects in the decays of resonances are also discussed.

The present state of the general theory of response functions of material media, describing the universal properties of these functions that characterize all types of medium, is surveyed. Topics covered include recent results on the range of admissible values of static permeability, the form of the Landau functional for the electrodynamic ordering of a medium, and the electrodynamics of a medium interacting with a magnetic monopole. Applications to high-temperature superconductivity, anomalous diamagnetism, and monopole detection are discussed.

An analysis has been made of the linear response of polarization to a uniform change in temperature, in its gradient (thermal polarization effect), in macroscopic deformation and in its gradient (flexoelectric effect). It has been shown how the use of some definitions of polarization widespread in the literature can lead to essentially incorrect results in the analysis of piezo- and flexoelectric effects in the field of elastic deformations of an acoustic wave. It has also been shown that in calculating the above responses in the case of a spatially uniform disturbance in a sample of finite size two classes of contributions arise: 1) contributions depending on the microscopic properties of the lattice, and 2) contributions depending only on changes in the distortion tensor accompanying the response, and on multipole moments of the charge distribution of the whole unperturbed crystal. In this connection it was established that the former contributions are bulk effects while the latter ones are surface or false contributions (which are not manifested in the generally accepted experimental arrangements for measurements). The special features of the manifestation of the flexoelectric and thermal polarization effects are discussed in detail.

Phenomena occurring at the interface of liquid crystals with other (solid, liquid, and gaseous) phases are reviewed. The basic parameters of the macroscopic surface physics of thermotropic liquid crystals are studied: the adhesion energy, the surface order parameter, and the surface polarization; the basic methods for determining them experimentally are described. A great deal of attention is devoted to methods for obtaining a uniform orientation of liquid crystals. The role of the surface in phase transitions is analyzed in detail. The effect of the interface on the formation and structure of defects in liquid crystals is described. The role of van der Waals forces in the orientation of liquid crystals and in local Fredericks transitions is analyzed.

The review describes modern achievements of the physics of plasma—wall interactions in tokamaks. The main methods allowing a reduction of the energy of the particles incident on the first wall and, thus, important for the prevention of wall erosion, are described in an easily understandable form. The conditions required for the formation of strong near-wall material recycling are briefly considered. The heat and mass transport processes in the peripheral region of the plasma as well as electric arc discharges on walls of tokamaks are discussed.

Studies are reviewed on the development and applications of a new method of recording optical spectra that preserves full information on both the amplitude and phase relationships between the spectral components of the light field being recorded, and which thus realizes "holographic spectroscopy." The method has been realized in practice in various polarization modifications of Coherent Active (anti-Stokes) Raman Spectroscopy (CARS). By using it, the problem has been solved in principle of resolving close, overlapping spectral lines not amenable to discrimination by the Rayleigh criterion in noncoherent spectra. In polarization CARS the experimenter can carry out a controlled action on the form and amplitude of an optical resonance being recorded ("multidimensionality" of spectra). However, this is not accompanied by an actual distortion of the spectrum or action from the probe field on the object of study. The principles of holographic spectroscopy have been realized experimentally, and by using them new information has been obtained on the internal structure of broad superposed Raman and light-absorption lines.

An active transformation of a physical system implies its motion. A passive transformation of the system is a change in the method of describing it. An analogy transformation means transition to another physical system, similar in some respect to the original one. In some cases transformations of one type may imitate those of another. The operation of particle permutation in quantum mechanics implies a passive transition to describing the same state of the system by a different method of introducing particle numbering. The problems of transitions from describing identical particles to describing different ones and that of "explaining" the probabilistic meaning of wave functions statistically are touched upon.