Table of contents

Considering a pulse-like ansatz, we derive different classes of exact soliton solutions of the modified complex Ginzburg–Landau equation. We then present the important variations which occur in the domain of stability of these solutions depending on the values of the renormalization coeffecients. This means that this term which can be considered for nonzero solutions and which does not generally occur in the literature could explain the lack of concordance between some theory and experiments.

The propagation of dust ion acoustic waves (DIAWs) in a collisionless, unmagnetized inhomogeneous dusty plasma containing cold positive ions, cold positive and negative dust grains, and isothermal electrons is theoretically studied. Nonlinear DIAWs are shown to be governed by a variable coefficient Kortewege–de Vries (KdV) equation. At the critical density of ions both compressive and rarefactive modified KdV solutions co-exist. Below (above) this critical point the system supports rarefactive (compressive) solitons.

In this study, we consider two models of two dimensional (2D) discrete systems subjected to three different types of coupling and analyse systematically the performance of each in realizing synchronized states. We find that linear coupling (CS1) effectively introduces control of chaos along with synchronization, while synchronized chaotic states are possible with an additive parametric coupling (CS3) scheme both being equally relevant for specific applications. The basin leading to synchronization in the initial value plane and the choice of parameter values for synchronization in the parameter plane are isolated in each case.

Spin properties of free charge carriers in PbTe and PbSe are analysed using for this purpose the concept of spin surface, which in the simplest case reduces to the Bloch sphere. It is shown that in lead chalcogenides the spin surfaces are ellipsoids, the principal axes of which depend on the charge carrier wave vector, spin–orbit interaction strength, and the basis functions used to construct the Hamiltonian. The present results may be useful in the study of dynamics of the polarized charge carriers injected electrically or optically into the volume of PbTe, PbSe or PbS.

The amplitude of wake fields generated by the finite-width laser pulse propagating in an underdense plasma are determined using weakly nonlinear equations (n'_e≪n₀) for triangular (TR) and two types of sawtooth (SD and SI, defined in section 2) pulses by making the pulse duration the same as the electron plasma period. In addition to density perturbations n_e', the potential ϕ and the wake field E_z behind the laser pulses, the expression for the change in relativistic factor γ or energy gain for an electron is obtained and discussed for all these types of laser pulses under the effect of laser frequency f, pulse duration τ (corresponding to plasma density n₀) and laser intensity I₀. The TR pulse is found to be most significant as in this case the electrons can be accelerated up to hundreds of MeV (471.6 MeV) when τ = 6 ps, I₀ = 1.0×10¹² W m⁻² and f = 282 THz (corresponding to Nd:YAG laser of wavelength 1.064 μm); even more acceleration is possible with prudently selected parameters.

An experimental study is carried out on the effect of chemical admixtures, particularly sodium chloride, on the energy absorption behaviour of a hydrophobic nanoporous silica. As the pressure increases, once the capillary effect is overcome, the liquid is forced into the nanopores; and when the pressure is reduced, outflow is difficult, resulting in a pronounced hysteresis. The inflow pressure and the specific absorbed energy are strongly dependent on the sodium chloride concentration, providing a promising way to adjust the system performance.

A few years ago a hopeful article (Evans 2000 Phys. Scr.61 513–7) appeared in this journal promising that according to its 15 authors' opinion the pending energy crisis could be solved by 'extracting energy from the vacuum'. However, in the past years the energy price has grown to unthinkable heights: a reason for having a look at the promised 'energy from the vacuum' in (Evans 2000). So we shall do so below and shall arrive at a great disappointment: the 15 authors were in error; their vacuum energy stems from a simple flaw of thinking by misinterpreting the well-known Lorenz term of the classical Maxwell gauge theory. Their miraculous conclusion should have made the authors suspicious, that just the Lorenz term should yield a vacuum current. Surely, its a pity that vacuum currents and vacuum energy in (Evans 2000) have their origin merely in a simple flaw of thinking, and all further speculations for a vacuum energy density are in vain. However, better to return to reality.

Quote: Abstract of [1]: Great announcements...

It is shown that if the Loren(t)z condition is discarded, the Maxwell–Heaviside field equations become the Lehnert equations, indicating the presence of charge density and current density in the vacuum. The Lehnert equations are a subset of the O(3) Yang–Mills field equations. Charge and current density in the vacuum are defined straightforwardly in terms of the vector potential and scalar potential, and are conceptually similar to Maxwell's displacement current, which also occurs in the classical vacuum. A demonstration is made of the existence of a time dependent classical vacuum polarization which appears if the Loren(t)z condition is discarded. Vacuum charge and current appear phenomenologically in the Lehnert equations but fundamentally in the O(3) Yang–Mills theory of classical electrodynamics. The latter also allows for the possibility of the existence of vacuum topological magnetic charge density and topological magnetic current density. Both O(3) and Lehnert equations are superior to the Maxwell–Heaviside equations in being able to describe phenomena not amenable to the latter. In theory, devices can be made to extract the energy associated with vacuum charge and current.

The paper (Evans 2000 Phys. Scr. 61 287–91) 'On the nature of the B⁽³⁾ field' essentially refers to a hypothesis that was proposed in 1992 by M W Evans: Evans claimed that a so-called O(3)-symmetry of electromagnetic fields should exist due to an additional constant longitudinal 'ghost field' B⁽³⁾ accompanying the well-known transversal plane em waves. Evans considered this symmetry, a fixed relation between the transversal and the longitudinal amplitudes of the wave, as a new law of electromagnetics. In the paper (Evans 2000) in this journal the authors claim 'that the Maxwell–Heaviside theory is incomplete and limited' and should be replaced with Evans' O(3)-theory the centre of which is Evans' O(3)-symmetry law. Later on, since 2002, this O(3)-symmetry became the centre of Evans' CGUFT which he recently renamed as ECE theory. A law of physics must be invariant under admissible coordinate transforms, namely under Lorentz transforms. A plane wave remains a plane wave also when seen from arbitrary other inertial systems. Therefore, Evans' O(3)-symmetry law should be valid in all inertial systems. To check the validity of Evans' O(3)-symmetry law in other inertial systems, we apply a longitudinal Lorentz transform to Evans' plane em wave (the ghost field included). As is well-known from SRT and recalled here the transversal amplitude decreases while the additional longitudinal field remains unchanged. Thus, Evans' O(3)-symmetry cannot be invariant under (longitudinal) Lorentz transforms: Evans' O(3)-symmetry is not a valid law of physics. Therefore it is impossible to draw any valid conclusions from that wrongO(3)-hypothesis. The paper (Evans 2000) has no scientific basis.

In 1992, M W Evans proposed a so-called O(3) symmetry of electromagnetic fields by adding a constant longitudinal 'ghost field' to the well-known transversal plane em waves. He considered this symmetry as a new law of electromagnetics. Later on, since 2002, this O(3) symmetry became the centre of his Generally Covariant Unified Field Theory which he recently renamed as ECE Theory. One of the best-checked laws of electrodynamics is the principle of linear superposition of electromagnetic waves, manifesting itself in interference phenomena. Its mathematical equivalent is the representation of electric and magnetic fields as vectors. By considering the superposition of two phase-shifted waves we show that the superposition principle is incompatible with M W Evans' O(3) hypothesis.

A detailed study of the characteristics of cloud-to-ground (CG) lightning flashes over Sweden was carried out for the period 1987–2000 using data obtained from the Swedish lightning-locating network. Results are presented by analysing over half a million lightning ground flashes. The average variation of the annual mean of the total number of flashes was found to be 37%. About 12% of the CG flashes were positive flashes and their average variation about the annual mean was 26%. The average peak currents were fairly constant over the years with variations as little as 4% for negative flashes and 5% for positive flashes. The average peak current values for negative and positive flashes were −29.90 and +63.97 kA respectively. A correlation between the mean monthly flash count and percentage of positive flashes was seen. A similar relationship is seen with the mean monthly flash count and the peak currents for both polarities. In general, high flash density and high peak currents were observed in the southern part of Sweden where most of the major cities are located. Flash densities exceeding 0.4 flashes km⁻² were observed for several large cities. The maximum flash rate of 32 flashes h⁻¹ within a 10 km radius was seen in Jönköping (14.18°E, 57.78°N) in the province of Småland.

Electron paramagnetic resonance (EPR) and optical studies of VO(II) doped cadmium sodium sulphate hexahydrate (CSSH) are carried out at room temperature. The EPR spectra, recorded in the three orthogonal planes, indicate that the paramagnetic impurity has entered the lattice site both in substitutional and interstitial positions. The spin Hamiltonian parameters, calculated from the spectra for the two sites, are: site I: g_xx=1.984, g_yy=1.975, g_zz=1.938; A_xx=6.56, A_yy=7.50, A_zz=18.61 mT; site II: g_xx=1.982, g_yy=1.978, g_zz=1.940; A_xx=6.88, A_yy=7.56, A_zz=18.57 mT. The EPR spectrum of the powder sample also reveals the presence of two sites in the host lattice, suggesting that the two sites are chemically and magnetically inequivalent. The optical absorption spectrum exhibits three characteristic bands. Crystal field, tetragonal field, admixture coefficients and bonding parameters are evaluated, which suggest that the complex is fairly covalent in nature.

In this study, we show that one cannot use non-local resources for probabilistic signalling even if one can delete a quantum state with the help of a probabilistic quantum deletion machine (PQDM). Here, we find that PQDM is not going to help us in identifying two statistical mixtures at a remote location. Also we derive the bound on deletion probability from a no-signalling condition.

The influence of the number of accounted admixed configurations on the accuracy of the energy spectra of the ground and four excited configurations (1s²2s2p⁵ and 1s²2s²2p³3l) as well as on the radiative lifetimes of the excited levels is investigated. The five ions (Mg V, Si VII, Cl X, Ca XIII and Cr XVII) of the oxygen isoelectronic sequence are taken as examples. The calculations are performed on the basis of the transformed radial orbitals. The admixed configurations are selected according to their influence evaluated in the second order of perturbation theory.

In this paper, we study the evolution of two two-level atoms interacting with a single-mode quantized radiation field, namely, the two-atom multiphoton Jaynes–Cummings model (JCM). We assume that the field and the atoms are initially prepared in the superposition of displaced number states and excited atomic states, respectively. For this system, we investigate the atomic inversion, Wigner function, phase distribution and entanglement. We show that for symmetric (asymmetric) atoms, the system can generate asymmetric (symmetric) cat states at a quarter of the revival time. Furthermore, the degrees of entanglement for the field–atoms and the one-atom–remainder tangles depend on the rate of energy flow between the parties. The interference in phase space decreases the degree of entanglement in the bipartite.

A theoretical scheme for quantum secure direct communication (QSDC) is proposed, where a three-qubit symmetric W state functions as a quantum channel. Two legitimate communicators can transmit their secret information by using quantum teleportation and local measurements.

Using a simple model of fermions interacting with a strong short range repulsive potential, we discuss how short range correlations can be described with a linear combination of Slater determinants using variational methods. The many-body wavefunction obtained in this way is used to evaluate the two-particle correlation function which shows the typical depletion at distances between particles comparable with the range of the repulsive potential.

Many activated phenomena, including solid state diffusion in crystals and polymers, dielectric relaxation, conduction and thermally stimulated processes in polymers, and electronic conduction in amorphous semiconductors, obey the compensation law or Meyer–Neldel rule. In the present paper, we report the compensation effect in the isothermal crystallization of glassy Se_80−xGe₂₀In_x (0 ⩽ x ⩽ 20) and Se_78−xGe₂₂Bi_x (0 ⩽ x ⩽ 10) alloys. We have observed the Meyer–Neldel rule between the preexponential factor K₀ and the activation energy of crystallization E_c in the present case.

In this paper, firstly, the general projective Riccati equation method (PREM) is applied to derive variable separation solutions of the (2 + 1)-dimensional Boiti–Leon–Pempinelli (BLP) equation. By further studying, we find that these variable separation solutions, which seem independent, actually depend on each other. Based on the variable separation solution and by selecting appropriate multi-valued functions, novel interactions between a special bell-like semi-foldon and a special peakon-like semi-foldon are investigated.

We study the synchronization in a ring of mutually coupled electromechanical devices. Each device consists of an electrical Duffing oscillator coupled magnetically with a linear mechanical oscillator. By varying the coupling coefficient, we find the ranges for cluster and complete synchronization, either in the regular state or in the chaotic one. Effects of this coupling parameter show various types of bifurcation sequences.

We review how electronic and vibrational degrees of freedom become coupled in molecular photoionization, and describe effects that emerge as the molecular complexity increases. Molecular photoionization is frequently influenced by the temporary trapping of the continuum electron in the field of the target molecules, which is referred to as a shape resonance, as it depends on the shape of the potential experienced by the exiting photoelectron. Such resonances couple electronic and vibrational motion, and the nature of the coupling can vary widely for polyatomic molecules. We show how vibrationally resolved photoelectron spectra acquired as a function of energy can be used to elucidate such coupling. The experiments are analysed using physically realistic and computationally tractable Schwinger variational theory, and the systems studied to date can be well understood using an independent-particle, adiabatic nuclei framework. As a result, simple and intuitive pictures emerge, even when dealing with scattering phenomena involving complex molecular targets and potentials.