Vitalii L. Ginzburg

Macroscopic theory of superconductors with small coherence length

Abstract Macroscopic theory for superconductors with small coherence length is developed.

On the theory of superfluidity of helium II near the ? point

The present state of the Ψ theory of superfluidity of helium II near the λ point is reviewed. The basic assumptions underlying this theory and the limits of its applicability are discussed. The results of the solution of some problems in the framework of the theory are presented and compared with experimental data. The necessity and possibility of further comparison of the theory with experiment are emphasized.

Origin of cosmic rays: Galactic models with halo

Many years ago physical and radio-astronomical arguments and data led to the assumption that cosmic rays in the Galaxy (and probably in other galaxies) fill a more or less extended halo, but are not concentrated in the disk. It was not so long ago, however, that the existence of a radio-halo was discovered, in which the effective dimensions increase with a decrease in frequency. The frequency decrease occurs when relativistic electrons diffuse from the disk, losing energy due to bremsstrahlung and Compton scattering.Meanwhile, some ambiguity on the question of the existence of a radio-halo, and other reasons, have led to a rather wide use of disk models, particularly those in which cosmic rays are present in the Galaxy only for a periodTcr,d≲3×106 yr. The authors have repeatedly stated the inadmissibility of such models and, generally, a homogeneous (leaky box) model for the origin of cosmic rays. The new data concerning the amount of radioactive10Be nuclei in cosmic rays near the Earth in no way contradict the halo models in which the lifetime of cosmic rays isTcr,h∼108 yr. In connection with the continuing controversy, the present paper is devoted to a detailed consideration of the difference between the homogeneous and diffusion models. Within the latter models some calculations on the chemical composition of cosmic rays have been carried out, which concern not only stable but also radioactive isotopes.

Coherent mechanisms of radio emission and magnetic models of pulsars

This paper is primarily concerned with the questions of models and the mechanisms of radio emission for pulsars, the polarization of this radiation and related topic. For convenience and to provide a more complete picture of the problems involved, a short summary of the data on pulsars is also given.Besides the introduction, the paper contains the following sections:(2)Some Facts about Pulsars.(3)The Astrophysical Nature of Pulsars.(4)Coherent Mechanisms of Radio Emission from Pulsars.(5)Models of Pulsars: Magnetic, Pulsating White Dwarfs and Neutron Stars.(6)The Polarization of the Radio Emission from Pulsars.(7)A Synthesized Model of Pulsars — Magnetic, Pulsating and Rotating Neutron Stars.(8)Concluding Remarks.

ON THE NATURE OF QUASARS AND ACTIVE GALACTIC NUCLEI

Attractive features and difficulties of the most widely held concepts on the energy sources in quasars and active galactic nuclei (a supermassive rotating magnetoplasmic body, an accreting black hole, a compact star cluster) are reviewed and discussed. In the light of the available data (particularly of recent results on the character of optical variability in a number of objects) models of a compact star cluster seem improbable. The concept of a magnetoid is less vulnerable, but the final choice between magnetoid and accreting black hole will be possible only after the details of these models have been thoroughly elaborated, and when new observational data become available.

Excitation and radiation of an accelerated detector and anomalous doppler effect

Abstract The excitation of a uniformly accelerated detector moving in a vacuum has been widely discussed in recent years. The aim of the present paper is to point out that such an excitation and the associated radiation are similar to those occuring in the region of anomalous Doppler effect which takes place when a detector is moving at a constant superlight velocity in a medium.

Thermoelectric current in a superconducting circuit

The problem of a thermoelectric current in a closed circuit of two different superconductors is considered. A solution is found that describes the distribution of field and currents about the cross section of a long nonuniformly heated, inhomogeneous cylinder. The generally accepted model for the current distribution (see Ref. 1 for a Review) is shown to be valid and the conclusions of Pickett to be erroneous. The connection of the theory to experiment is discussed.

On the role of plasma effects in the cosmic ray propagation and isotropization in the Galaxy

Cosmic ray (c. r.) propagation in interstellar magnetic fields is often considered in the diffusion approximation, i.e. by the diffusion equation in the coordinate space. Cosmic ray momentum distribution in this case is considered isotropic when the space gradients of c.r density are absent. This approach, with the use of an unfixed effective diffusion coefficientD independent of the energyE enables one to describe all the data available However, neither the diffusion mechanism nor the limits of applicability of the diffusion approximation is clear particularly ifD is independent ofE. Furthermore, the diffusion coefficientD must be expressed through the characteristics of the interstellar medium and possibly through the flux velocity and density of c.r. etc. One of the possible approaches for the analysis of the mechanism and characteristic features of c.r. distribution and isotropization is the account taken of the plasma effects and specifically, the study of c.r. flux instability arising when c.r. are moving in the interstellar plasma. As a result of such instability c.r. may generate waves of different types (magnetohydrodynamic, high-frequency plasma and other waves). Generation of waves and scattering on them result in isotropization of cosmic rays while their propagation under certain conditions turns out similar to that under diffusion.An attempt is made here to systematically analyse the avove mentioned plasma effects and to find out to what extent they are responsible for the behaviour of c.r. in the Galaxy. It turns out that c.r. In any case this is true if this mechanism is regarded as the only c.r. isotropization mechanizm within a wide energy range from 1 to 1000 GeV. Isotropization and spatial diffusion of c.r. up toE∼100–1000 GeV on the waves from external sources (for example, on the waves from the supernova shells) also proved impossible if the diffusion coefficient is assumed to be independent of c.r. energy. Some new possibilities of c.r. isotropization are also considered.

The radiation of electromagnetic waves and the instability of electrons moving at super-light velocity in a medium

Abstract The features of the radiation of electromagnetic waves by particles or systems (atoms, molecules, etc.) moving in a medium or near a medium (the moderating system) at super-light velocity can often be successfully analysed by applying quantum considerations, even when the problem is a classical one. This is also the case for the radiation, absorption and amplification of waves in beams of particles, and for the study of their instability. We shall discuss questions of this kind in this paper, including the problem of the classical force of reaction of the radiation when a charge moves in a medium. Our basic result, which follows from both simple quantum considerations and classical calculations, is as follows: when the motion is at super-light velocity, the radiation reaction force which changes the amplitude of oscillation of a particle decreases, and in some cases even changes sign, i.e. responds to the building up of oscillations and not to ‘friction’. In accordance with this fact, when beams ...

Some problems of gamma-astronomy

The modern state of gamma-ray astronomy is reviewed, the paper being mainly devoted to the theoretical models that describe generation of gamma-ray emission under astrophysical conditions. Basic information on the processes of generation and absorption of gamma-rays, as well as the results of observations for various gamma-ray photon energies are reported.In the region of soft gamma-ray emission (i.e., for energies less than tens of MeV), where emission in gamma-ray lines dominates, we also discuss the nature of gamma-ray bursts, the origin of gamma-ray emission from the galactic centre, etc.Discrete sources and, in particular, the mysterious source Cyg X-3 are discussed in the region of very high (Eγ > 1012 eV) and ultra-high (Eγ > 1015 eV) energy gamma-ray emission.A larger portion of the review is devoted to the analysis of cosmic-ray origin on the basis of the available gamma-ray data in the region from several tens of MeV to several GeV. The peculiarity of this energy range is, in particular, in the fact that the diffuse galactic emission was observed mainly there. We also discuss the problem of determination of the cosmic-ray density gradient from the gamma-ray data.The origin of high-latitude gamma-ray emission, the problem of galactic gamma-ray halo, etc., are discussed.The theoretical models explaining the nature of unidentified gamma-ray sources, as well as the results of measurements and theoretical estimations of a gamma-ray flux from SN1987A are analysed.