Characteristics of Surface Spin Waves in a Metal–Dielectric–Ferrite–Dielectric–Metal Structure

The dispersion and isofrequency characteristics of surface spin waves in a tangentially magnetized metal–dielectric–ferrite–dielectric–metal structure are investigated. A loop-like change in the isofrequency dependences for spin waves is observed in a certain range of frequencies, and the origin of the loop is always located at wave number value k → 0.     

On a relation of the angular frequency to the Aharonov–Casher geometric phase in a quantum dot

By analysing the behaviour of a neutral particle with permanent magnetic dipole moment confined to a quantum dot in the presence of a radial electric field, Coulomb-type and linear confining potentials, then, an Aharonov–Bohm-type effect for bound states and a dependence of the angular frequency of the system on the Aharonov–Casher geometric phase and the quantum numbers associated with the radial modes, the angular momentum and the spin are obtained. In particular, the possible values of the angular frequency and the persistent spin currents associated with the ground state are investigated in two different cases.     

Dispersion of Bulk Waves in a Graphene–Dielectric–Graphene Structure

Optics and Spectroscopy - We investigate the dispersion properties of the first waveguide modes in a dielectric film that is coated with graphene layers having different chemical potential values....     

Non-singular space-times with a negative cosmological constant: II. Static solutions of the Einstein–Maxwell equations

We construct infinite-dimensional families of non-singular static space-times, solutions of the vacuum Einstein–Maxwell equations with a negative cosmological constant. The families include an infinite-dimensional family of solutions with the usual AdS conformal structure at conformal infinity.     

Theory of atomic–molecular conversion under the conditions of Bose–Einstein condensation

A set of nonlinear differential equations that describe the dynamics of atomic–molecular conversion under the action of two arbitrarily shaped Raman pulses of resonance laser radiation has been derived in the mean-field approximation. The dynamics of the system subjected to Gaussian pulses has been studied in detail. It has been shown that the time evolution of the system depends on the initial conditions.     

Model of the unsteady two-phase three-component filtration of the oil–water–supercritical fluid system in a homogeneous porous medium

A mathematical model of the two-phase three-component filtration of the oil–water–supercritical fluid system in a porous medium is developed. The results of numerical simulations of the three-component two-phase filtration during oil displacement by supercritical CO₂ from a watered stratum are reported. In the region of oil displacement from watered stratum, there is a significant discrepancy between the experimental and simulation results because of the transient mode of filtration associated with the concurrent saturation of the oil and water with supercritical CO₂ under high pressure. In the region of two-phase filtration of the oil–water system and in the region of pumping of three or more pore volumes of supercritical CO₂, the deviation of the simulation results from the experimental data does not exceed 10%.     

On the relation of the Methagalaxy mass to the gravitation constant. 1. from Einstein’s theory to the Einstein–Cartan theory

The notion of the dimensionless gravitational charge defined through the Planck mass and the fundamental constants specifying this mass itself is introduced. The Big Bang is related to the unified physical interaction decay and the drop of Newton’s gravitational constant by 40.67 orders of magnitude in comparison with the electromagnetic constant taken as unity. This causes an increase in theMetagalaxy curvature radius by the same value and a decrease in the average density of space–time curvature sources by 122 orders of magnitude: from the maximum allowable Planck density to the observed critical density. The microphysics appears naturally related to cosmology.     

Equilibrium vortex lattices of a binary rotating atomic Bose–Einstein condensate with unequal atomic masses

We perform a detailed numerical study of the equilibrium ground-state structures of a binary rotating Bose–Einstein condensate with unequal atomic masses. Our results show that the ground-state distribution and its related vortex configurations are complex events that differ markedly depending strongly on the strength of rotation frequency, as well as on the ratio of atomic masses. We also discuss the structures and radii of the clouds, the number and the size of the core region of the vortices, as a function of the rotation frequency, and of the ratio of atomic masses, and the analytical results agree well with our numerical simulations. This work may open an alternate way in the quantum control of the binary rotating quantum gases with unequal atomic masses.     

Is the light velocity in vacuum really a constant? Possible breakdown of the linear ω-k relation at extremely high frequencies

We investigate the novel problem of what happens in special relativity and in relativistic field theories whenthree-dimensional space is quantized. First we examine the equation for elastic waves on a linear chain, the simplest example of a quantized medium, and propose, on its analogy, a nonlinearp-k relationp=k(sinhkl)/kl for light and material waves. Here,kl is a new variable which represents the space-quantization effect on the plane wave of wave numberk=|k|. (Note thatkl=0 givesp=k.) This relation makes the light velocity in vacuum dependent onkl. We postulate, however, that the phase and group velocities of each individual light wave are still invariant, and try to generalize special relativity to the case ofkl 0. This can be simply done if the invariance ofkl is assumed. Our results suggest that localization might be a relative concept. One interesting consequence of our proposal is that relativistic field theories become automatically finite. This comes out without violating unitarity or causality. A precise measurement of velocities of high-energy photons or massive particles is desirable for checking our proposal.     

Reduced aliasing formulations of the convective terms within the Navier–Stokes equations for a compressible fluid

The effect on aliasing errors of different formulations describing the cubically nonlinear convective terms within the discretized Navier–Stokes equations is examined in the presence of a non-trivial density spectrum. Fourier analysis shows that the existing skew-symmetric forms of the convective term result in reduced aliasing errors relative to the conservation form. Several formulations of the convective term, including a new formulation proposed for cubically nonlinear terms, are tested in direct numerical simulation (DNS) of decaying compressible isotropic turbulence both in chemically inert (small density fluctuations) and reactive cases (large density fluctuations) and for different degrees of resolution. In the DNS of reactive turbulent flow, the new cubic skew-symmetric form gives the most accurate results, consistent with the spectral error analysis, and at the lowest cost. In marginally resolved DNS and LES (poorly resolved by definition) the new cubic skew-symmetric form represents a robust convective formulation which minimizes both aliasing and computational cost while also allowing a reduction in the use of computationally expensive high-order dissipative filters.     

Specific Features of the Structure and the Dielectric Properties of Sodium–Bismuth Titanate-Based Ceramics

The phase formation, specific features, and the dielectric properties of the ceramics of compositions from the region of morphotropic interface in the (Na_0.5Bi_0.5)TiO₃–BaTiO₃ system modified by Bi(Mg_0.5Ti_0.5)O₃ and also low-melting additions KCl, NaCl–LiF, CuO, and MnO₂ that favor the control of the stoichiometry and the properties of the ceramics have been studied. The ceramics are characterized by ferroelectric phase transitions that are observed as jumps at temperatures near 400 K and maxima at T_m ~ 600 K in the temperature dependences of the dielectric permittivity. The phase transitions at ~400 K demonstrate the relaxor behavior indicating the existence of polar domains in the nonpolar matrix. An increase in the content of Bi(Mg_0.5Ti_0.5)O₃ favor a decrease in the electrical conductivity and dielectric losses of the samples, and the relative dielectric permittivity at room temperature ε_rt is retained quite high, achieving the highest values ε_rt = 1080–1350 in the ceramics modified with KCl.     

High-sensitivity measurements of the Kerr constant in gases using a Fabry–Pérot-based ellipsometer

The electromagnetic and geometric characteristics of electron beams generated by molybdenum cathodes illuminated by an excimer laser are reported. To determine the electromagnetic characteristics, a fast Rogowski coil was utilized, while the geometric characteristics were performed by a suitable slit–slit meter system. During the experiment the laser spot on the cathode was fixed to 4 mm². The maximum output current (370 mA) was reached with 0.5 mJ laser energy and 50 kV accelerating voltage. In these conditions the electron beam normalized emittance was 6 (π mm mrad) calculated at 80% level current density. The laser used in this experiment was a singular excimer laser (KrCl) operating in the NUV range. Received: 22 March 2000 / Revised version: 11 July 2000 / Published online: 5 October 2000     

Exact and asymptotic solutions of the Cauchy–Poisson problem with localized initial conditions and a constant function of the bottom

In the paper, the asymptotic solutions for a problem of Cauchy–Poisson type with localized initial conditions are constructed. The bottom of the basin under consideration which was constant before the perturbation, is instantly perturbed at the initial time moment by a spatially localized function. Simplifications of the corresponding formulas are presented inside and outside the vicinity of the leading front, as well as in the case of a special choice of the initial condition. It is shown that, in the vicinity of the leading front, the asymptotic solution coincides with the asymptotic solution of the linear Boussinesq equation.     

Ionization of molecules at the fluid–fluid phase transition in warm dense hydrogen

The problem of the fluid–fluid phase transition in warm dense hydrogen/deuterium has been studied experimentally and theoretically in the best laboratories in the last decade. However, the nature of the phase transition remains unclarified. In this paper we put forward the new idea that H₂ molecules are ionized at the phase transition to produce molecular H ₂ ⁺ and H ₃ ⁺ ions     

The Cosmological constant and the coincidence problem in a new cosmological interpretation of the universal constant “c”

In a recent paper (Vigoureux et al. in Int. J. Theor. Phys. 47:928, 2007) it has been suggested that the velocity of light and the expansion of the universe are two aspects of one single concept connecting space and time in the expanding universe. It has then be shown that solving Friedmann’s equations with that interpretation (and keeping c=constant) can explain number of unnatural features of the standard cosmology (for example: the flatness problem, the problem of the observed uniformity in term of temperature and density of the cosmological background radiation, the small-scale inhomogeneity problem…) and leads to reconsider the Hubble diagram of distance moduli and redshifts as obtained from recent observations of type Ia supernovae without having to need an accelerating universe. In the present work we examine the problem of the cosmological constant. We show that our model can exactly generate Λ (equation of state P _φ =−ρ _φ c ² with Λ∝ R ⁻²) contrarily to the standard model which cannot generate it exactly. We also show how it can solve the so-called cosmic coincidence problem.     

Liquid–vapour transition of the long range Yukawa fluid

Two liquid state theories, the self-consistent Ornstein–Zernike equation (SCOZA) and the hierarchical reference theory (HRT) are shown, by comparison with Monte Carlo simulations, to perform extremely well in predicting the liquid–vapour coexistence of the hard-core Yukawa (HCY) fluid when the interaction is long range. The long range of the potential is treated in the simulations using both an Ewald sum and hyperspherical boundary conditions. In addition, we present an analytical optimized mean field theory which is exact in the limit of an infinitely long-range interaction. The work extends a previous one by C. Caccamo, G. Pellicane, D. Costa, D. Pini, and G. Stell, Phys. Rev. E 60, 5533 (1999) for short-range interactions.     

A Combined Model of Charging of the Surface and Bulk of a Dielectric Target by Electrons with the Energies 10–30 keV

Russian Physics Journal - A physico-mathematical model of the processes of radiation-induced charging of dielectric materials with open surfaces, irradiated with monoenergetic electrons in the...     

Self-Action Effects in the Propagation of Surface Magnetostatic Wave Pulses in a Magnonic Crystal–Dielectric–Metal Structure

Technical Physics - We have analyzed the self-action effects in the propagation of surface magnetostatic wave (SMSW) pulses in a 1D magnonic crystal–dielectric–metal structure in which...