Showing papers in "Physics-Uspekhi in 1996"
TL;DR: In this paper, the anomalous baryon number nonconservation at high temperatures and in high energy collisions is reviewed and applications to electroweak baryogenesis are considered, and the current status of the problem of instanton-like processes at high energies is outlined.
Abstract: We review recent progress in the study of the anomalous baryon number non-conservation at high temperatures and in high energy collisions. Recent results on high temperature phase transitions are described, and applications to electroweak baryogenesis are considered. The current status of the problem of electroweak instanton-like processes at high energies is outlined. This paper is written on the occasion of Sakharov’s 75th anniversary and will appear in the memorial volume of Uspekhi (Usp. Fiz. Nauk, volume 166, No 5, May 1996).
424 citations
TL;DR: In this paper, the basic theory of the wavelet transform, an effective investigation tool for inhomogeneous processes involving widely different scales of interacting perturbations, is presented, and the analysis of a number of El Nino events and of the temporal behaviour of the Southern Oscillation index reveals periodic components, local periodicity features and time scales on which self-similarity structures are seen.
Abstract: The basic theory of the wavelet transform, an effective investigation tool for inhomogeneous processes involving widely different scales of interacting perturbations, is presented. In contrast to the Fourier transform, with the analysing function extending over the entire axis of time, the two-parametric analysing function of the one-dimensional wavelet transform is well localised in both time and frequency. The potential of the method is illustrated by analysing familiar model series (such as harmonic, fractal, and those with various types of singularities) and the long-term variation of some meteorological characteristics (Southern Oscillation index and global and hemispheric temperatures). The analysis of a number of El Nino events and of the temporal behaviour of the Southern Oscillation index reveals periodic components, local periodicity features and time scales on which self-similarity structures are seen. On the whole, both stochastic and regular components seem to be present. The global and hemispheric temperatures are qualitatively similar in structure, the main difference — presumably due to the greater amount of land and stronger anthropogenic factor — being that the warming trend in the Northern Hemisphere is slightly stronger and goes first in time.
304 citations
TL;DR: In this article, a review of crystallographic, magnetic and electric properties of lanthanum manganites and related materials with a giant magnetoresistance (GMR) is given.
Abstract: A review is given of crystallographic, magnetic and electric properties of lanthanum manganites and related materials with a giant magnetoresistance (GMR). An analysis of experimental data for partially substituted manganites shows that if the spontaneous magnetic moment is unsaturated, the material is being in a phase-separated ferro-antiferromagnetic state. One possible GMR mechanism consists in a change of such a state under the magnetic field. If the magnetic moment of these materials is saturated, they display a resistivity peak in the vicinity of the Curie point. It is caused by the interaction of the charge carriers with spatial fluctuations of the electric potential and local magnetization. Suppression of this peak by the magnetic field leads to a GMR in ferromagnetic conductors.
203 citations
TL;DR: It is shown that synchronisation plays a key role in the activity of both minimal neural networks (neural pair) and neural assemblies with a large number of elements (cortex).
Abstract: The construction of a dynamical theory of neural networks has been a goal of physicists, mathematicians and biologists for many years now. Experimental breakthroughs in modern neurobiology have allowed researchers to approach this goal. Significant advances have been made for small neural networks, which are generators of the rhythmic activities of living organisms. The subject of the present review is the problem of synchronisation, one of the major aspects of the dynamical theory. It is shown that synchronisation plays a key role in the activity of both minimal neural networks (neural pair) and neural assemblies with a large number of elements (cortex).
134 citations
TL;DR: In this paper, the Vavilov-Cherenkov effect, the transition radiation, and some other phenomena are discussed, including the VAVILOV-CHENkov effect and transition radiation.
Abstract: The radiation produced by uniformly moving sources (the Vavilov-Cherenkov effect, the transition radiation, and some other phenomena) is discussed. This area of physical research originated in the Lebedev Physical Institute of the Russian Academy of Sciences and now represents an integral part of modern physics.
123 citations
TL;DR: In this article, the influence of laser radiation with a wide range of deposited energies on a variety of processes is considered: these processes include crystal growth, formation of dissipative (spatial and temporal) defect structures on the surface and in the bulk of a solid, instabilities in melts, materials fracture considered from the point of view of both selectivity and selforganisation.
Abstract: The large amount of information carried by the energy, spectral, and space–time characteristics of a laser beam makes it feasible to use laser radiation to control the processes that occur in solids. The influence of laser radiation with a wide range of deposited energies on a variety of processes is considered: these processes include crystal growth, formation of dissipative (spatial and temporal) defect structures on the surface and in the bulk of a solid, instabilities in melts, materials fracture considered from the point of view of both selectivity and self-organisation. An analysis is made of the relationship between the nature and parameters of such structures, on the one hand, and the characteristics of laser radiation, on the other.
102 citations
TL;DR: The current status of research on coherent light backscattering, temporal and spatial correlations of intensity of light propagating through a randomly inhomogeneous medium, and coherent effects due to the multiple scattering from very rough surfaces are reviewed in this article.
Abstract: The current status of research on coherent phenomena in multiple light scattering from disordered systems is reviewed. The coherent light backscattering, temporal and spatial correlations of intensity of light propagating through a randomly inhomogeneous medium, and coherent effects due to the multiple scattering from very rough surfaces are considered. The present-day theories as well as methods and results of experimental studies are outlined. Almost all theoretical predictions are found to be illustrated well by respective experimental data.
99 citations
TL;DR: The state of the art of Monte Carlo studies of randomly modulated optical waves in regular and randomly inhomogeneous nonlinear media is reviewed in this article, where a wide range of phenomena dealt with in nonlinear statistical optics are discussed, including self-phase noise pulse modulation, the selfaction of partially coherent beams, the formation and instability of solitons, stimulated Raman scattering, intensive light beams in a turbulent atmosphere, and adaptive radiation focusing.
Abstract: The state of the art of the Monte Carlo studies of randomly modulated optical waves in regular and randomly inhomogeneous nonlinear media is reviewed. A wide range of phenomena dealt with in nonlinear statistical optics are discussed, including self-phase noise pulse modulation, the self-action of partially coherent beams, the formation and instability of solitons, stimulated Raman scattering, intensive light beams in a turbulent atmosphere, and adaptive radiation focusing. Special attention is given to the justification of the phase screen model for a randomly inhomogeneous nonlinear continuum, and the numerical simulation of random light fields is discussed in detail.
89 citations
TL;DR: In this article, the authors reviewed the results of quantum field renormalisation group results of the theory of developed turbulence, and the dimension of composite operators and the infrared asymptotic behaviour of various correlation functions are discussed.
Abstract: Quantum field renormalisation group results of the theory of developed turbulence are reviewed. Background information about quantum field renormalisation theory, including operator expansion and the renormalisation of composite operators is given. As an example problem, the stochastic model of isotropic homogeneous turbulence is considered for which, using the renormalisation technique, the existence of infrared scaling with Kholmogorov dimensions is proved. The dimension of composite operators and the infrared asymptotic behaviour of various correlation functions are discussed, and numerical amplitude factors of scaling laws are calculated.
78 citations
TL;DR: In this article, a systematic operational approach is presented to study the nonclassical light (NCL) using two parallel sets of numbers measured: probabilities of photocounts and normalised factorial moments of counts.
Abstract: Properties of the nonclassical light (NCL) have been considered with an emphasis on experimentally-observed features, which are underlain by the well-known Mandel's formula connecting the statistics of photocounts with that of light falling on the detector. A systematic operational approach is presented to study the NCL using two parallel sets of numbers measured: probabilities of photocounts {pm} and normalised factorial moments of counts {gk}. Two particular examples are examined in detail: a 'heated' squeezed vacuum and a 'heated' one-photon state. An alternative method is proposed to discover the week nonclassicality using 'generalised' moments {ak(s)}. The effect of the linear absorption (amplification) and of the beam-splitting of the NCL, and the relation between the NCL and the absolute calibration of photodetectors are considered. The conditions are elucidated whereat the beam-splitter realises a mathematical operation of superposition of two one-mode fields useful in studying the NCL.
74 citations
TL;DR: The state of the art of the problem of the analytical continuation of wave fields is reviewed and a computational algorithm for field singularities is given and the relation between the singularities and the 'computational catastrophes' of scattering models is discussed.
Abstract: The state of the art of the problem of the analytical continuation of wave fields is reviewed. The problem is a multi- disciplinary subject which involves radiophysics, acoustics, and opticsontheonehand,andmathematicalphysicsandthetheory of differential equation, on the other. The qualitative aspects of the problem are examined. A computational algorithm for field singularities is given. The relation between the singularities and the 'computational catastrophes' of scattering models is dis- cussed. To illustrate the theoretical material, numerous exam- ples are discussed in great detail.
TL;DR: In this article, a mathematical model for a phenomenological description of the global demographic process and to project its trends into the future is presented, assuming the growth rate to be proportional to the square of the number of people.
Abstract: Of all global problems world population growth is the most significant. Demographic data describe this process in a concise and quantitative way in its past and present. Analysing this development it is possible by applying the concepts of systems analysis and synergetics, to work out a mathematical model for a phenomenological description of the global demographic process and to project its trends into the future. Assuming self-similarity as the dynamic principle of development, growth can be described practically over the whole of human history, assuming the growth rate to be proportional to the square of the number of people. The large parameter of the theory and the effective size of a coherent population group is of the order of 105 and the microscopic parameter of the phenomenology is the human lifespan. The demographic transition — a transition to a stabilised world population of some 14 billion in a foreseeable future — is a systemic singularity and is determined by the inherent pattern of growth of an open system, rather than by the lack of resources. The development of a quantitative nonlinear theory of the world population is of interest for interdisciplinary research in anthropology and demography, history and sociology, for population genetics and epidemiology, for studies in evolution of humankind and the origin of man. The model also provides insight into the stability of growth and the present predicament of humankind, and provides a setting for discussing the main global problems.
TL;DR: In this paper, the history of creation and schemes of Arzamas-16 explosive laboratory devices for dynamical compressibility measurements at pressures up to 2.5 TPa are described, in which a thin, metallic impactor of spherical geometry is accelerated by the explosion products in converging detonation waves.
Abstract: History of creation and schemes of Arzamas-16 explosive laboratory devices for dynamical compressibility measurements at pressures up to 2–2.5 TPa are described, in which a thin, metallic impactor of spherical geometry is accelerated by the explosion products in converging detonation waves. The iron shock adiabat obtained with these devices over the period from 1948 to the early 60s and used as a dynamical standard in megabar and terapascal compressibility studies of other substances, is presented. In deriving its parameters for up to 10 TPa, iron compressibility data from underground nuclear explosions of the 70s, and calculated results from the modified quantum-statistical model have been employed.
TL;DR: In this paper, the quasi-isotropic approximation (QIA) of geometrical optics is outlined. The main idea of the method is that electromagnetic waves in weakly anisotropic media preserve their transverse structure as they do in isotropic media.
Abstract: The quasi-isotropic approximation (QIA) of geometrical optics is outlined. The main idea of the method is that electromagnetic waves in weakly anisotropic media preserve their transverse structure as they do in isotropic media. Advantages of the QIA are illustrated by considering electromagnetic wave propagation in plasma, a number of optical problems (liquid crystals, hiral media, single mode optical fibres), acoustical problems of weakly anisotropic elastic media, and quantum mechanical polarisation effects of the Stern–Gerlach type. New modifications of the QIA are presented, namely the method of split rays and the synthetic approach, the latter being applicable even for strongly anisotropic media.
TL;DR: In this paper, it is suggested that the role of a weak magnetic sublattice is played by the spin-ordered subsystem of hopping electrons, and the appearing point TB is nothing else but the low-temperature transformation point Tt(100-120 K).
Abstract: Measurements on the anomalous temperature behaviour of the spontaneous magnetisation in various ferrimagnets (N-, M-, and P-type Neel curves) are analysed and summarised. The concept of a 'weak' magnetic sublattice is applied to explain the anomalies as well as manifestations of the 'low-temperature point' TB and the antiferromagnetic-type paraprocess. The paraprocess phenomenon causes sign anomalies in the magnetocaloric effect, magnetostriction, and the 'first' component of the isotropic magnetoresistance. It is suggested that in magnetite (Fe3O4) the role of a 'weak' sublattice is played by the spin-ordered subsystem of hopping electrons ('magnetoelectron' sublattice), and the appearing point TB is nothing else but the low-temperature transformation point Tt(100-120 K).
TL;DR: In this paper, the transition radiation of elastic waves generated by a mechanical object that performs a uniform rectilinear motion along an inhomogeneous elastic system (a string, beam, membrane, or plate) is discussed in detail.
Abstract: Transition radiation of elastic waves generated by a mechanical object that performs a uniform rectilinear motion along an inhomogeneous elastic system (a string, beam, membrane, or plate) is discussed in detail. The effect is analysed by assuming that the law of motion of the load admits the generation of neither Cherenkov nor bremsstrahlung radiation, and that the role of inhomogeneties is played by the supports of the elastic system. The radiation reaction spectrum and the loss of contact between the object and the elastic system are considered.The practically important cases of periodically and randomly varying elastic parameters are examined, and the resonance and instability conditions for the vibrations of the radiating object are found. Variation of the main radiation characteristics with the angle at which the object crosses the inhomogeneity region, is examined. The so-called diffraction radiation of elastic waves is briefly discussed.
TL;DR: In this paper, the inductive-resonant mechanism of nonradiative transitions between electronic levels in lanthanide and transition metal ions and complex molecules in the condensed phase is systematically described.
Abstract: The inductive-resonant mechanism of nonradiative transitions between electronic levels in lanthanide and transition metal ions and complex molecules in the condensed phase is systematically described. A quantum-mechanical justification is presented, and theoretical expectations conforming to the mechanisms and quantitative rate constants of nonradiative transitions are compared with experiment.
TL;DR: In this article, the history of the discovery and investigation of cosmic rays prior to the advent of the cosmic ray astrophysics is presented and some data about cosmic rays near the Earth and in the Universe are given.
Abstract: The history of the discovery and investigation of cosmic rays prior to the advent of the cosmic ray astrophysics is presented. Some data about cosmic rays near the Earth and in the Universe are given. The main part of cosmic rays observed near the Earth is generated in our Galaxy by supernova explosions. The most important problem yet to be solved in cosmic ray astrophysics is the origin of cosmic rays of superhigh energy.
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TL;DR: In this article, current spectroscopic data on dimers and their ions are presented and analyzed. Methods for obtaining such data are discussed. And the authors present a method to obtain such data.
Abstract: Current spectroscopic data on dimers (molecules consisting of two similar atoms) and their ions are presented and analysed. Methods for obtaining such data are discussed.
TL;DR: In this paper, an analysis of the electronic structure of highly nonctoichiometric transition-metal carbides in both ordered and disordered states is given, which explains the influence of atomic and vacancy order on the physical properties of the carbides.
Abstract: An analysis of the electronic structure of highly nonctoichiometric transition-metal carbides in both ordered and disordered states is given, which explains the influence of atomic and vacancy order on the physical properties of the carbides. It is shown that the dependence of carbide properties on the arrangement of carbon atoms in the nonmetal sublattice is related to both the symmetry space group of the crystal and the symmetry of the nearest-neighbour environment of the carbide atoms. By analysing order–disorder phase transition data, experimental information on atomic and vacancy order in carbides is obtained in order to explain the nature of superstructures at high vacancy concentrations.
TL;DR: In this paper, the formation mechanisms for spatially nonuniform temperature and charged particle density distributions in a low-temperature gas discharge plasma are reviewed and conditions for the occurrence of, and parameter distributions in, the constricted state of the discharge are analyzed.
Abstract: Formation mechanisms for spatially nonuniform temperature and charged particle density distributions in a low-temperature gas discharge plasma are reviewed. Conditions for the occurrence of, and parameter distributions in, the constricted state of the discharge are analyzed. Spatial temperature and electron density distributions and the pressure and power-input dependence of the plasma column radius are determined in local thermodynamic equilibrium. Special attention is given to a cluster-containing plasma. For this new type of spatially nonuniform discharge plasma, the cluster growth process is studied and the limiting cluster size is evaluated. The potential application of the cluster plasma as an illumination source is assessed and performance characteristics of such a source are calculated.
TL;DR: In this paper, a review of the results of the comet impact with Jupiter is discussed and a unified physical model is suggested which explains consistently the basis observational data, including the formation of large-scale long-lived vortex structures in the Jovian atmosphere.
Abstract: In July 1994, a dramatic event took place—the collision of the Shoemaker–Levy 9 comet with Jupiter. This collision has been accompanied by a great number of various effects in the atmosphere, ionosphere and magnetosphere of Jupiter. The comet impact became one of the most grandiose active experiments Nature has ever performed. Among the most interesting effects are bursts of radiation registered in a wide spectral range during the cometary fragments fall, the generation of giant gaseous plumes caused by impact, the formation of large-scale long-lived vortex structures in the Jovian atmosphere. Unexpected events were the significant brightening of the Jovian radiation belts during the cometary fragments impact, the peculiarities of polar aurorae induced by the impact, the weakening of the Io plasma torus brightness observed in the extreme UV range, etc. In the present review, the results of the comet impact with Jupiter are discussed and a unified physical model is suggested which explains consistently the basis observational data.
TL;DR: In this article, a spin-wave approximation theoretical analysis of orthoferrite magnetoacoustics is presented, accounting as fully as possible for interactions between all the subsystems involved, including the ordered ferrous, elastic, paramagnetic rare-earth, and dipole (electromagnetic) subsystems.
Abstract: Experimental and theoretical work on the magnetoacoustics of rare-earth orthoferrites near reorientation phase transitions (RPTs) is reviewed. The temperature and field dependence of magnetoresonant soft-mode frequencies and of the sound velocity and attenuation near various RPTs, as obtained by RF and ultrasonic spectroscopy, are given. A spin-wave approximation theoretical analysis of orthoferrite magnetoacoustics is presented, accounting as fully as possible for interactions between all the subsystems involved, including the ordered ferrous, elastic, paramagnetic rare-earth, and dipole (electromagnetic) subsystems. The origin of energy gaps in the spin-wave spectrum is discussed in detail, as are the ultrasonic dispersion, propagation velocity, and attenuation changes at RPT points. The energy gaps measured and the sound velocity behaviour observed are shown to result from the interaction of the orthoferrite subsystems. In most cases experimental data agree well with theoretical predictions.
TL;DR: In this article, the concept of the "norm of chaos" ('norm of order') was introduced and used to differentiate degradation and self-organization processes in open systems, with special reference to a criterion for the relative degree of order in nonequilibrium states of such systems.
Abstract: Main concepts of a new interdisciplinary research area known as 'Physics of Open Systems' are introduced with special reference to a criterion for the relative degree of order in nonequilibrium states of such systems. Based on this criterion, the notion of the 'norm of chaos' ('norm of order') is proposed and used to differentiate between degradation and self-organization processes. The possibility of applying methods of open system physics to investigations in economics, sociology and physiology is briefly discussed.
TL;DR: The genesis and historical background of the hydrogen bomb are described in this article, with particular emphasis placed on the development of the physical ideas which led to the discovery of the basic principle of thermonuclear charge construction in the USA and USSR.
Abstract: The genesis and historical background of the hydrogen bomb are described, with particular emphasis placed on the development of the physical ideas which led to the discovery of the basic principle of thermonuclear charge construction in the USA and USSR.
TL;DR: Neutron time-of-flight diffractometry provides an effective and rapidly developing method for current neutron diffraction studies and has great prospects owing of the construction of new high-flux neutron sources producing either pulsed or continuous beams as discussed by the authors.
Abstract: Neutron time-of-flight diffractometry provides an effective and rapidly developing method for current neutron diffraction studies. It has great prospects owing of the construction of new high-flux neutron sources producing either pulsed or continuous beams. The authors discuss specific potentialities of the method for structural studies. Special attention is paid to recently evolved lines of research including correlation neutron diffractometry, kinetic processes, the use of high pressure, external electric and magnetic fields.
TL;DR: In this paper, the authors reviewed the current hypotheses concerning the breaking of mirror symmetry in the bioorganic world and discussed two interrelated aspects of the problem, matrix-structured homochiral macromolecules and enantiospecific functions capable of keeping homchiral structures replicating, and two basic approaches to symmetry breaking, namely evolutionary selection and asymmetric origin scenarios, are considered.
Abstract: Current hypotheses concerning the breaking of mirror symmetry in the bioorganic world are reviewed critically. Two interrelated aspects of the problem, matrix structured homochiral macromolecules and enantiospecific functions capable of keeping homochiral structures replicating, are discussed. Two basic approaches to symmetry breaking, namely evolutionary selection and asymmetric origin scenarios, are considered, whose underlying hypotheses are shown to be inherently inconsistent.
TL;DR: In this article, a unified interpretation of the radial velocity and optical light curves allows one to reliably justify the close binary system model and to prove the correctness of determination of the optical star mass function fv(m).
Abstract: Mass determination methods and their results for ten black holes in X-ray binary systems are summarised. A unified interpretation of the radial velocity and optical light curves allows one to reliably justify the close binary system model and to prove the correctness of determination of the optical star mass function fv(m).The orbit plane inclination i can be estimated from an analysis of optical light curve of the system, which is due mainly to the ellipsoidal shape of the optical star (the so-called ellipticity effect). The component mass ratio q = mx/mv is obtained from information about the distance to the binary system as well as from data about rotational broadening of absorption lines in the spectrum of the optical star. These data allow one to obtain from the value of fv(m) a reliable value of the black hole mass mx or its low limit, as well as the optical star mass mv. An independent estimate of the optical star mass mv obtained from information about its spectral class and luminosity gives us test results. Additional test comes from information about the absence or presence of X-ray eclipses in the system. Effects of the non-zero dimension of the optical star, its pear-like shape, and X-ray heating on the absorption line profiles and the radial velocity curve are investigated. It is very significant that none of ten known massive (mx > 3M) X-ray sources considered as black hole candidates is an X-ray pulsar or an X-ray burster of the first kind.