Table of contents

A study is made of the interaction of a random field of electromagnetic radiation with the free electrons of a plasma, with applications to astrophysical problems, in particular the theory of how thermodynamic equilibrium of the radiation in a hot universe is established. A kinetic equation describes the variation of the spectrum; special attention is devoted to induced scattering and the classical interpretation of induced energy and momentum transfer. In the spectra of radio sources with a high luminosity temperature, induced scattering can lead to a Bose condensation of photons, a shock wave and solitons. The scattering of strong low-frequency waves is considered in connection with their effect on pulsars and laboratory coherent generators.

Analysis of the physical properties of surfaces should be based on the maximum possible amount of information deduced from studies of the propagation of surface rather than volume electromagnetic waves, in which the energy is transported only along surfaces or separation boundaries between media. The present review, therefore, discusses a broad range of problems in the crystal optics of surface electromagnetic waves (surface polaritons), a subject developed in the course of the last few years. Various theoretical and experimental methods of investigating surface waves in crystals are discussed and compared, including a detailed review of Raman scattering of light. Other topics discussed include different effects in the spectra of surface waves due to the transition layer, the role of damping and spatial dispersion, the transformation of surface into volume waves, and so on. Possible fields of future research are suggested.

Various formulations of problems in the statistical theory of diffraction and wave propagation are discussed: excitation of fields by random sources, diffraction of partially coherent waves, diffraction of waves by bodies having random shapes or positions, and diffraction and propagation of waves in a randomly inhomogeneous medium. For each of these types of problem, physical problems from acoustics, radio astronomy, radiophysics, optics, and other branches of physics are given as examples, and the methods (mostly approximate ones) most widely used for solving them are indicated. Among the problems discussed are those of the diffraction content of the radiation transport equation and the back scattering enhancement effect observed in the diffraction of waves by small bodies immersed in a randomly irregular medium. Examples of statistical problems of mixed type are also given.

This review is concerned with the structure, electrical, and optical properties of mixed-valence platinum complexes of the K₂ Pt(CN)₁, Br_0.303H₂O type and of TTF-TCNQ salts. Special attention is paid to the experimental results on the anisotropy of electron motion in these quasi-one-dimensional crystals. The theory of the Peierls metal-insulator transition is considered for a one-dimensional system in the molecular field approximation, allowing for statistical fluctuations of the order parameter. It is shown that the Peierls transition is associated with the appearance of a giant Kohn anomaly in the phonon spectrum. The experimental results confirming the occurrence of the Peierls transition in platinum complexes (structure data, paramagnetic susceptibility, and phonon spectrum) are analyzed from the theoretical point of view. An analysis is also made of the influence of three-dimensional effects and of the disorder in crystals on the Peierls transition. The possibility of the Peierls transition in TTF-TCNQ is considered and the problem of the paraconductivity resulting from this transition is discussed.

A number of refinements in ground-based optical telescopes and their detecting equipment, and also serious development of measures for neutralization of interference effects of the earth's atmosphere, permit the efficiency of observation of faint astronomical objects to be improved by at least an order of magnitude in the coming years. In the case of extragalactic astronomy and observational cosmology it is shown that progress in large ground-based optical telescopes has a decisive role in formation of contemporary concepts of the universe. Some of the problems of astronomy which will be solved by means of these instruments in the near future are discussed.