Table of contents

We study ellipse-shaped solitons on top of a stable continuous-wave background in the framework of a two-dimensional nonlinear Schrödinger equation with Kerr and saturable nonlinearities. We show that both dark and anti-dark elliptic solitons may exist, and examine their dynamics in detail, for different values of the initial eccentricity, amplitude and radius. Strictly speaking, all the elliptic solitons are unstable; however, in many cases they persist for a long time, and may be observed experimentally in nonlinear optics and Bose–Einstein condensates.

This paper is concerned with magnetic monopole solutions of SU(3) Yang–Mills–Higgs systems beyond the Bogomol'nyi–Prasad–Sommerfield limit. The different SU(2) embeddings, which correspond to the fundamental monopoles, as well as the embedding along composite root are studied. The interaction of two different fundamental monopoles is considered. Dissolution of a single fundamental non-BPS SU(3) monopole in the limit of minimal symmetry breaking is analysed.

Multiconfiguration Dirac–Fock calculations have been carried out in the Extended Optimal Level (EOL) scheme on the energies, transition probabilities and weighted absorption oscillator strengths of intercombination lines of highly ionized argon. The calculations have been carried out in intermediate coupling with empty K shell, varying degrees of ionization in the L shell and open outer shells. The radiative transition rates have been calculated in both length and velocity gauges and an analysis on the accuracy of the orbital functions used in this work has been attempted by comparing the length form and velocity form transition rates.

Sheared flow generation is investigated in one dimensional hybrid simulations (kinetic ions/fluid electrons) of imploding plasmas. Examples in both Cartesian and cylindrical (z pinch, θ pinch, screw pinch) geometries are described. It is shown that sheared flow is generated consistent with off-diagonal terms in the collisionless pressure tensor for all cases. These terms result from large Larmor radius ions interacting with the moving plasma-vacuum boundary. The effects of changing the rate of implosion and initial ion orbits through adjustment of the initial ion inertial length (λ_si) were investigated. It was found that the amount of flow generated is maximum when the rate of implosion was maximum and for a specific range of λ_si in each case.

The radiative drift-Alfvén wave instability in a nonuniform dusty magnetoplasma has been theoretically studied by using a normal mode analysis. A new dispersion relation has been derived analytically, and studied numerically in order to examine the instability of the drift-Alfvén waves. The roles of the net heat radiation loss, electron collision frequency, inhomogeneities in plasma temperature and densities, the presence of static dust (impurities), etc. on the drift-Alfvén wave instability have been discussed. The results of this theoretical investigation can have relevance to the instabilities in low-β fusion plasma devices (tokamaks).

Electrostatic low frequency surface waves propagating on the planar interface between a dusty plasma and vacuum are investigated taking into account ion-neutral, ion-dust and neutral-dust collisions as well as ionization. Both the temporal and spatial attenuation rates and the damping of the dust-acoustic surface modes due to collisions and ionization are derived.

Theoretical models for Mach cones in magnetized dusty plasmas of Saturn's rings are presented. Dispersion properties of different types of longitudinal and transverse waves (viz. dust–acoustic waves, fast and slow dust–magnetoacoustic waves) in magnetized dusty plasmas are presented. Numerical results are presented for V_d/V_p (> 1), which determines the existence of Mach cones as well as their opening angles [θ = sin^-1(V_p/V_d)], where V_d is the dust boulder speed and V_p ( = ω/k) is the phase speed of short or long wavelength disturbances in magnetized dusty plasmas. It is found that short wavelength (in comparison with the ion gyroradius) modified dust–acoustic waves and long wavelength slow dust–magnetoacoustic waves (DMW) are viable candidates for the formation of Mach cones in the equatorial plane of Saturn's rings. They should be observed by on board instruments of the CASSINI spacecraft that is supposed to enter Saturn's orbit in July 2004.

The effect of axial energy spread on the linear gain in a Backward Wave Oscillator is considered. The electron beam is assumed to be monoenergetic with a momentum spread. The results obtained are used to discuss the effects of a finite spread in the beam axial momentum on the BWO instability and frequency of electromagnetic wave generation.

I develop here a semi-microscopic quantum theory for description of creation of phonons and rotons in superfluid helium by a solid heater. Starting with a correct transfer Hamiltonian describing a coupling between solid and liquid ⁴He the probabilities of transformation of a single phonon in the solid into (i) single helium phonon, (ii) two helium phonons, and (iii) single helium roton are found out. All the obtained expressions account for different polarizations of phonons in the solid. The heat transfer associated with single phonon and single roton channels are calculated. Particularly, the obtained expression for heat flux via the single phonon channel calculated in the framework of present microscopic theory coincides exactly with the well known Khalatnikov formula obtained initially in the framework of acoustic-mismatch theory. The impossibility of direct creation of R^(-) rotons becomes clear in the used framework due to accurate account of the boundary conditions at the solid–liquid helium interface, which is in agreement with recent experimental results.

The treatment of GaAs (001) surface with different thicknesses of Mg layers has been studied. When Mg is deposited onto GaAs, the Mg immediately penetrates the top layers of the GaAs where interaction occurs between Mg and GaAs to form an impurity paired with a Mg interstitial. This change in the bonding state of Ga and As in the diffusion layers removes Ga or As intensity from the bulk peaks and moves it into the Ga or As shifted peaks. This in turn accounts for the very low effective mean free path. Further deposition of Mg forms a layer on the surface whose thickness increases with continued deposition. Deposition of Mg resulted in slight shifts for the Ga and As core levels. The chemical shift between the bulk core level and the new bond is 1 eV towards lower binding energy for the Ga case and 0.41 eV for the As case. A value of 0.43 nm has also been obtained for the inelastic scattering mean free path for electrons with kinetic energy 65 eV in the Mg layers. After 15 min annealing at 500 °C, all core levels from the substrate slightly shift back upward to the binding energy. Meanwhile, the new chemically shifted component in the Ga core level was fully desorbed but the Mg core level was still observed.

We analyze the origin and character of dynamical effects in electron tunneling in planar metal–insulator–metal systems evaluating semiclassically a path integral expression for the tunneling amplitude. A transparent connection between the interaction of the tunneling electron with the quantized charge fluctuations and the effective one-electron potential is made. For the first time a comparison between the local and nonlocal parts of the effective potential for the electron tunneling for zero and finite temperatures is explicitly analyzed in a single approach. The situations when local and nonlocal parts, always of opposite sign, are comparable in strength are found and discussed.

An exact solution around a global monopole resulting from the breaking of a global S0(3) symmetry in Kalb–Ramond background is found. The monopole exerts no gravitational force on non-relativistic matter, but the space around it has a deficit solid angle.

We review the status of and comment on current developments in the field of two-photon decay in atomic physics research. Recent work has focused on two-photon decays in highly-charged ions and two-photon decay of inner-shell vacancies in heavy neutral atoms. We emphasize the importance of measuring the shape of the continuum emission in two-photon decay as a probe of relativistic effects in the strong central fields found in heavy atomic systems. New experimental approaches and their consequences will be discussed.

The general profile of a resonance, as given by Fano in 1961, is well known throughout physics. This Comment provides some of the simplest derivations of this formula, together with a discussion of subtleties in handling continuum states with regard to their normalization, orthogonality, and completeness. Inadequate appreciation of these subtleties has led to misconceptions and errors in analysis. Recent, novel applications of the Fano formula in condensed matter systems include systems with decoherence and lack of time reversal symmetry which make the resonance profile parameter complex.