Showing papers in "Physics-Uspekhi in 1991"
TL;DR: In this article, the authors assume that the universe is neutral with respect to the conserved charges (lepton, electric, and combined), but asymmetrical during the given instant of its development.
Abstract: This form of notation is connected with the quark concept; we ascribe to the/?, n, and Л quarks n c = + I, and to antiquarks, и,. = — 1. The theory proposes that under laboratory conditions processes involving violation of п в and и д play a negligible role, but they were very important during the earlier stage of the expansion of the universe. We assume that the universe is neutral with respect to the conserved charges (lepton, electric, and combined), but С asymmetrical during the given instant of its development (the positive lepton charge is concentrated in the electrons and the negative lepton charge in the excess of antineutrinos over the neutrinos; the positive electric charge is concentrated in the protons and the negative in the electrons; the positive combined charge is concentrated in the baryons, and the negative in the excess of fi neutrinos over/z antineutrinos). According to our hypothesis, the occurrence of С asymmetry is the consequence of violation of CP in variance in the nonstationary expansion of the hot universe during the superdense stage, as manifest in the difference between the partial probabilities of the charge-conjugate reactions. This effect has not yet been observed experimentally, but its existence is theoretically undisputed (the first concrete example, I, + and 2 _ decay, was pointed out by S. Okubo as early as 1958) and should, in our opinion, have much cosmological significance. We assume that the asymmetry has occurred in an earlier stage of the expansion, in which the particle, energy, and entropy densities, the Hubble constant, and the temperatures were of the order of unity in gravitational units (in conventional units the particle and energy densities were n~ 10
1,289 citations
TL;DR: In this article, the authors consider the problem of identifying the action (1) with the change in the action of quantum fluctuations of the vacuum if space is curved and consider the metrical elasticity of space as a sort of level displacement effect.
Abstract: The presence of the action (1) leads to a “metrical elasticity” of space, i.e., to generalized forces which oppose the curving of space. Here we consider the hypothesis which identifies the action (1) with the change in the action of quantum fluctuations of the vacuum if space is curved. Thus, we consider the metrical elasticity of space as a sort of level displacement effect (cf. also [1a]). In present-day quantum field theory it is assumed that the energy momentum tensor of the quantum fluctuations of the vacuum T k(0) and the corresponding action S(0), formally proportional to a divergent integral
301 citations
TL;DR: In this article, the influence of the interaction of the components on the differential probability of pair production was studied and it was shown that the interaction can influence the probability of pairing production.
Abstract: The influence of the interaction of the components on the differential probability of pair production is studied.
124 citations
TL;DR: In this article, a hyperbolic transport equation that is a special case of these local-nonequilibrium equations is used for the analysis of traveling waves having high velocities.
Abstract: Transport equations are studied for two types of media exhibiting properties of local nonequilibrium: media with thermal memory and media with a discrete structure. A hyperbolic transport equation that is a special case of these local-nonequilibrium equations is used for the analysis of traveling waves having high velocities. These waves have certain important properties: there can be a temperature discontinuity at the wave front; there exist thermal shock waves; the temperature at the wave front exceeds the equilibrium adiabatic value; there exist stationary autowave regimes in addition to those corresponding to the classical local-equilibrium case, and the velocities of these regimes are bounded by the velocity of propagation of a thermal signal. The approach developed here may be useful for the study of transport processes for short times or high fluxes in systems near critical points, in heterogeneous systems, and in other extremal situations.
99 citations
TL;DR: In this paper, it is conjectured that there exist states of the physical continuum which include regions with different signatures of the metric and that the observed Universe and an infinite number of other Universes arose as a result of quantum transitions with a change in the signature of the metrics.
Abstract: It is conjectured that there exist states of the physical continuum which include regions with different signatures of the metric and that the observed Universe and an infinite number of other Universes arose as a result of quantum transitions with a change in the signature of the metric. The Lagrangian in such a theory must satisfy conditions of non-negativity in the regions with even signature. Signature here means the number of time coordinates. The induced gravitational Lagrangian in a conformally invariant theory of Kaluza-Klein type evidently satisfies this requirement and leads to effective equations of the gravitational theory of macroscopic space identical to the equations of the general theory of relativity. It is suggested that in our Universe there exist in addition to the observable (macroscopic) time dimension two or some other even number of compactified time dimensions. It is suggested that the formation of a Euclidean region in the center of a black hole or in the cosmological contraction of the Universe (if it is predetermined by the dynamics) is a possible outcome of gravitational collapse.
82 citations
TL;DR: In this article, standard invariant perturbative methods are used to derive an expression for the radiation-reaction force acting on a charged particle in quantum electrodynamics.
Abstract: Standard invariant perturbative methods are used to derive an expression for the radiationreaction force acting on a charged particle in quantum electrodynamics. When the average change in the particle's momentum is found by taking an average over the states closest to the classical state, the result is an expression whose classical limit is the same as the classical expression for the radiation-reaction force.
67 citations
TL;DR: In this article, an approximate approach to the description of complex space-time structures in different types of excitable media based on the kinematics of autowave fronts is proposed.
Abstract: We consider an approximate approach to the description of complex space-time structures in different types of excitable media based on the kinematics of autowave fronts. Because of the generality and relative simplicity of the kinematic approach, it is possible to obtain analytical results for different types of autowave motion in two and three-dimensional excitable media. The kinematic approach is used to treat steady-state autowave structures and also to study the evolution of autowaves in inhomogeneous, time-dependent and anisotropic media.
65 citations
TL;DR: In this paper, a survey of the current state of theoretical studies of two-dimensional dipole systems is presented, where the authors examine the orientational states of isolated radicals in local potentials of hindered rotation, various types of orientational ordering of dipoles in 2D lattices and the appearance of the dipole glass phase in a system with arbitrary filling of lattice sites by particles.
Abstract: This survey is devoted to the current state of theoretical studies of two-dimensional dipole systems. Systems of hydroxyl groups on the surfaces of oxides have been the most experimentally studied systems. The article examines the orientational states of isolated radicals in local potentials of hindered rotation, various types of orientational ordering of dipoles in twodimensional lattices, and the appearance of the dipole glass phase in a system with arbitrary filling of lattice sites by particles. Proof is presented of the existence of long-range order in twodimensional dipole systems, as well as estimates of phase transition temperatures. There is a discussion of the theory of the vibrational spectra of ordered and disordered systems of dipole radicals in various orientational phases. Experimental data are presented on the infrared spectroscopy of surface hydroxyl groups. The data verify theoretical results. Unresolved problems are indicated as well as the prospects for further studies of two-dimensional dipole systems.
59 citations
TL;DR: In this article, a review of wave packet generation and detection in Rydberg atoms and molecules is presented, where the time limits of applicability of the correspondence principle and wave packet collapse caused by nonlinear effects are considered.
Abstract: A review is presented of a new field in optical spectroscopy, in which the dynamics of wave packets composed of stationary states of atoms and molecules is studied. The time limits of applicability of the correspondence principle and wave packet collapse caused by nonlinear effects are considered. A new phenomenon is discussed, in which the wave packets are revived during their long-term post-classical evolution. Recent experiments on wave packet generation and detection in Rydberg atoms and molecules are reviewed. The experiments provide new opportunities for investigation of the transition region between classical and quantum physics of atomic particles. The relations between the phenomena discussed and the problem of generation of non-classical states of light in nonlinear optical systems is considered.
58 citations
TL;DR: In this paper, a natural system of fundamental physical units c,, and mP is discussed, where n is the velocity of light, is Planck's constant, andmP is the Planck mass, which is related to the Newtonian gravitational constant by the equation mP2 = c/G.
Abstract: A natural system of fundamental physical units c, , and mP is discussed, where n is the velocity of light, is Planck's constant, and mP is the Planck mass, which is related to the Newtonian gravitational constant by the equation mP2 = c/G. In a natural system of units, such questions as: "How does the anthropic nature of the physical universe arise? Is it unique, or does an infinite set of universes exist?" and "Are the fundamentals of the physical universe knowable and what is the strategy for knowing them?" become particularly urgent.
TL;DR: In this article, the problem of the selection of forms and scales of convective flows in a horizontal layer of liquid heated from below is studied, and the basic types of two-and three-dimensional flows, defects of roll structures, exchange of the convective regimes, and different situations in which two-dimensional rolls have a preferred wave number are described.
Abstract: The problem of the selection of forms and scales of convective flows in a horizontal layer of liquid heated from below is studied. The basic types of two- and three-dimensional flows, defects of roll structures, exchange of convective regimes, and different situations in which two-dimensional rolls have a preferred wave number are described. It is shown that when considered in terms of an optimal (preferred) wave number, to which a roll structure tends and which may or may not be reached depending on the overall geometry of the flow, the different experimental and theoretical results form a unified consistent picture. The basic methods used for investigation of convective structures are described.
TL;DR: In this paper, a review of the pattern formation problem in mobile micro-organism populations is devoted to an investigation of the nonlinear character of the processes which control the behavior of an individual organism.
Abstract: This review is devoted to an investigation of the pattern formation problem in mobile micro-organism populations. This pattern formation is due to the nonlinear character of the processes which control the behavior of an individual organism. Various examples of the pattern formation (population waves, swarms, Rayleigh?Taylor cells, green holes, etc.) are reviewed in detail. It is demonstrated that the stability of these patterns is due to the interaction between organism and environment. The importance of investigating the transformation from random motion of individual cells to determinate behavior of cellular collectives for progress in bioengineering is discussed.
Abstract: We discuss the geometrical theory of wave propagation in regularly inhomogeneous waveguide media from the point of view of nonlinear Hamiltonian dynamics. We consider ray dynamics in waveguides with periodic longitudinal inhomogeneities, including the phenomenon of spatial nonlinear resonance of rays, which leads to the formation of an effective waveguide channel in the neighborhood of the ray in resonance with the periodic inhomogeneities. We consider different properties of spatially resonant rays: the optical path length and propagation velocity of a signal along rays trapped in a separate nonlinear resonance; the fractal properties of rays, such as the devil's staircase form of the dependence of the spatial oscillation frequency of the ray and the propagation time of a signal along the rays. The trajectory of sound rays in a model of the ocean with transverse flow is considered using the adiabatic invariant method and the transverse drift of a ray with respect to the main propagation direction of sound is described. We consider the conditions for dynamical chaos of rays in a waveguide with longitudinal periodic inhomogeneities. We examine the conditions for internal spatial nonlinear resonance and chaos of rays in waveguides with an irregular cross section and their effect on the propagation velocity of a signal. We study the connection between the structure of the wave front and the dynamics of rays in waveguide channels with regular inhomogeneities. Finally, we discuss the applicability of geometrical optics in waveguides under the conditions of nonlinear resonance and chaos of rays, and the relation between this problem and quantum chaos.
TL;DR: In this article, the authors apply the theory of superconductors with overlapping energy bands to describe the thermodynamic and electromagnetic properties of the high-temperature compounds La2-x(Ba,Sr)xCuO4 and YBa2Cu3O7-δ.
Abstract: The possibility is indicated of applying the theory of superconductors with overlapping energy bands to describe the thermodynamic and electromagnetic properties of the high-temperature compounds La2–x(Ba,Sr)xCuO4 and YBa2Cu3O7–δ. The two-band model was used to obtain high values of Tc, two energy gaps 2Δ1/Tc > 3.5 and 2Δ2/Tc < 3.5, large negative values of d ln Tc/d ln V (V is the volume) in lanthanum ceramics, small values of the jump in the electron heat capacity at T = Tc, negative curvature of the upper critical magnetic field H2c near the transition temperature, etc. Such behavior of the above quantities is observed experimentally. A description is also obtained of the decrease in Tc as the disordering of oxygen increases, and also as copper atoms are replaced by a nonmagnetic impurity (Al, Zn, etc.). The main mechanism responsible for this decrease is the interband scattering of electrons by impurities and by randomly distributed oxygen vacancies. A theory has been developed of multiband superconductors which takes into account the points of high symmetry in momentum space. On the basis of this theory one can explain the existence of a plateau in the dependence of Tc on δ for YBa2Cu3O7–δ, and also in the dependence of Tc on x for La2–x(Ba,Sr)xCuO4, that has been observed in a number of experiments. Moreover this theory also explains the presence of two maxima in the dependence of Tc on pressure for Bi2Sr2CaCu2O8.
TL;DR: In this paper, a detailed review of numerical calculations that involve a single hole in the antiferromagnetic phase and are based on the Monte Carlo method and the exact diagonalization of small clusters is presented.
Abstract: Current ideas on the interaction between magnetic and superconducting states in strongly magnetized systems are discussed in terms of the Hubbard model and its limiting case in the form of the t – J model. Two approaches to the problem are compared, namely, those of weak and strong Coulomb repulsion, i.e., U W and U W, respectively, where U is the repulsion and W the electronic band width. The dynamic magnetic susceptibility of the system is analyzed in both cases, and different types of magnetic instability are identified. Spin fluctuations that grow near the instability boundaries of the paramagnetic phase give rise to Cooper instability. The role of longitudinal and transverse spin fluctuations in the evolution of the superconducting state in a magnetically ordered phase is also investigated. Particular attention is devoted to the two-dimensional model near half-filling. Analytic studies based on the generalized random phase approximation are presented. In addition, a detailed review is given of numerical calculations that involve a single hole in the antiferromagnetic phase and are based on the Monte Carlo method and the exact diagonalization of small clusters. The problem of two interacting holes is also examined. Such studies may provide the conceptual basis for magnetic (correlational) mechanisms of high-Tc superconductivity in copper oxide compounds.
TL;DR: In this article, a review on the methods of the theory of singularities applied to the Landau phenomenological theory of phase transitions is presented, and a set of algorithms are presented that eliminate arbitrariness in the choice of the potential and make it possible to exclude from consideration models with nonphysical results.
Abstract: A review is presented on the methods of the theory of singularities applied to the Landau phenomenological theory of phase transitions. Constructive algorithms are presented that eliminate arbitrariness in the choice of the Landau potential and make it possible to exclude from consideration models with nonphysical results. The methods of singularity theory are illustrated by application to several real thermodynamic systems.
TL;DR: A review of the results of the search for four-quark states in γγ collisions during the last decade is presented in this paper, where the resonance phenomena in the reactions are discussed in detail.
Abstract: A review of the results of the search for four-quark states in γγ collisions during the last decade is presented. The resonance phenomena in the reactions γγ → ρ0ρ0, γγ → ρ+ρ−, γγ → ωρ0, γγ → , γγ → ωω, γγ → V, γγ → π0η and γγ → ππ are discussed in detail. In particular, it is shown that presently there are telling arguments for observation of a tensor exotic resonance with isospin I = 2 near the ρρ threshold in γγ → ρ0ρ0 and γγ → ρ+ρ−. A set of new experiments for the elucidation of the physical nature of the considered phenomena is also suggested.
TL;DR: In this article, the Hamiltonian path integrals (HPI) is modified in the case of an arbitrary gauge group and the main attention is devoted to the correct formulation of the HPI with a poor choice of gauge.
Abstract: Publications on the structure of the physical phase space (PS) of dynamical systems with gauge symmetry are reviewed. The recently discovered phenomenon of reduction of the phase space of the physical degrees of freedom is studied systematically on mechanical models with a finite number of dynamical variables. In the simplest case of one degree of freedom this phenomenon consists of replacement of the phase space by a cone that is unfoldable into a half-plane. In the general case the reduction of the phase space is related with the existence of a residual discrete gauge group, acting in the physical space after the unphysical variables are eliminated. In "natural" gauges for the adjoint representation this group is isomorphic to Weyl's group. A wide class of modes with both the normal and Grassmann (anticommuting) variables and with arbitrary compact gauge groups is studied; the classical analysis and the quantum analysis are performed in parallel. It is shown that the reduction of the phase space radically changes the physical characteristics of the system, in particular its energy spectrum. A significant part of the review is devoted to a description of such systems on the basis of the method of Hamiltonian path integrals (HPIs). It is shown how the HPI is modified in the case of an arbitrary gauge group. The main attention is devoted to the correct formulation of the HPI with a poor choice of gauge. The analysis performed can serve as an elementary illustration of the well-known problem of copies in the theory of Yang–Mills fields. The dependence of the quasiclassical description on the structure of the phase space is demonstrated on a model with quantum-mechanical instantons.
TL;DR: The crystal structure of twenty structurally different types of high-temperature oxide superconductors is discussed in this article, followed by a detailed review of the phase relationships and the growth of single crystals belonging to the following systems.
Abstract: The crystal structure of twenty structurally different types of high-temperature oxide superconductors is discussed. This is followed by a detailed review of the phase relationships and the growth of single crystals belonging to the following systems: La–Sr–Cu–O, Ba–Y–Cu–O, Bi–Sr–Ca–Cu–O, Nd–Ce–Cu–O, Tl–Ba–Ca–Cu–O, Ba–K–Bi–O, and Ba–Rb–Bi–O.
TL;DR: Fractal filaments, which are fractal structures formed as a result of relaxation of a plasma evaporated from the surface of a metal in an external electric field, are considered in this paper.
Abstract: Fractal filaments, which are fractal structures formed as a result of relaxation of a plasma evaporated from the surface of a metal in an external electric field, are considered. The physical properties of systems of this kind, their formation under natural conditions, and potential applications are discussed.
TL;DR: In this paper, the authors discuss the history of the study of superconductivity and the discovery of high-temperature superconductors, the calculation of the critical temperature Tc of the superconducting transition and ways of increasing this temperature, and the mechanism that provides for high Tc values.
Abstract: An enormous number of scientific papers have been devoted to high-temperature superconductors. For this reason this report only touches upon certain topics. These topics include the history of the study of superconductivity and the discovery of high-Tc superconductivity, the calculation of the critical temperature Tc of the superconducting transition and ways of increasing this temperature, and the mechanism that provides for high Tc values. This report also examines the specific details of high-Tc superconductivity within the framework of the macroscopic theory of superconductivity and the question of thermocirculational thermoconductivity in high-Tc superconductors. Finally, a few comments are made concerning the future study of this topic.
TL;DR: In this article, a great deal of attention is devoted to the phenomenon of suppression of most spectral lines in the range corresponding to allowed transitions in vibronic spectra, and some reasons for this phenomenon are discussed.
Abstract: Different aspects of the theoretical interpretation and utilization of the fine-structure vibronic spectra of polyatomic organic molecules in solution for determining characteristics of the electronic excited states of such molecules, such as the orbital type, localization of excitation on fragments, change of nuclear configuration, etc., are presented. The adiabatic approximation with Frank–Condon and Herzberg–Teller coupling is studied. A great deal of attention is devoted to the phenomenon of suppression of most spectral lines in the range corresponding to allowed transitions in vibronic spectra. Some reasons for this phenomenon are discussed.
TL;DR: In this paper, the circulation heat transfer and the appearance of a thermoelectric superconducting current in anisotropic superconductors and in a super-conducting circuit are discussed.
Abstract: The thermoelectric effects which may be observed in the superconducting state are considered. The circulation heat transfer and the appearance of a thermoelectric superconducting current in anisotropic superconductors and in a superconducting thermoelectric circuit are discussed specifically. The special nature of the thermoelectric effects in high-temperature superconductors is stressed.
TL;DR: In this article, the problems of massive black holes in galactic nuclei of different types are reviewed and the dynamical evolution of compact star systems ends naturally in a gigantic concentrated mass of gas, containing an admixture of surviving stars, that unavoidably collapses into a black hole.
Abstract: The problems of massive black holes in galactic nuclei of different types are reviewed. The dynamical evolution of compact star systems ends naturally in a gigantic concentrated mass of gas, containing an admixture of surviving stars, that unavoidably collapses into a black hole. The subsequent joint evolution of the remnant star system with a massive black hole at the center leads either to the phenomenon of a bright central source in the nuclei of active galaxies and quasars or to the opposite case of a "dead" frozen black hole in the nucleus of a normal galaxy.
TL;DR: In this article, conditions of the thermal explosion and the character of propagation of thermal wave inside macroscopic fractal systems are analyzed and conditions of thermal explosion in aerogel and fractal fiber are analyzed.
Abstract: Macroscopic fractal systems, aerogel and fractal fiber, have a high specific surface energy. Mechanisms of the process of structure densification which leads to the transformation of the surface energy into thermal energy are considered. Transport processes inside macroscopic fractal systems are investigated. Conditions of the thermal explosion and the character of propagation of the thermal wave inside these systems are analyzed.
TL;DR: In this paper, it was shown that the formal application of the quantum relationship for a photon to the calculation of the flux density of the angular momentum yields false results, and that for a plane electromagnetic wave this quantity equals zero despite the opinion established in the literature.
Abstract: This paper discusses problems associated with the expressions for the angular momentum density and the flux density of the angular momentum of an electromagnetic wave within the framework of classical electrodynamics. We show that the formal application of the quantum relationships for a photon to the calculation of the flux density of the angular momentum yields false results. For a plane electromagnetic wave this quantity equals zero despite the opinion established in the literature. This conclusion does not contradict the possibilities of angular momentum transfer in the interaction of a circularly polarized wave with material objects. In particular, in the absorption of such a wave in a plasma, angular momentum is partly transferred to the electrons, and closed quasistationary electric currents arise. The process of generation of the magnetic field excited here possesses a number of distinctions from the inverse Faraday effect known in the literature.
TL;DR: A review of the use of holographic interferometry with regulated measurement sensitivity for transparent media diagnostics is given in this article, where a review is given of methods for increasing sensitivity during the multiple passage of a beam through a volume being investigated or a hologram.
Abstract: This is a review of holographic methods which enable one to regulate the sensitivity of interference measurements. Methods for increasing measurement sensitivity by using waves reconstructed from a hologram in higher diffraction orders and from a rerecording of a hologram, and also methods for regulating sensitivity that are based on recording holograms in two wavelengths, are considered. A review is given of methods for increasing sensitivity during the multiple passage of a beam through a volume being investigated or a hologram. Electronic phase measurement methods which enable one to increase the threshold of measurement sensitivity are considered. A review of the use of holographic interferometry with regulated measurement sensitivity for transparent media diagnostics is given.