[en] The theory of envelope solitons of surface waves in a thin slab of magnetized plasma in the case of strong static magnetic field is taken up in the present study

[en] Bulk properties of the exciton-polariton dispersion in the presence of a uniform electric field and for frequencies near the first excitonic resonance are studied within the framework of Stahl's coherent band dynamics. A relative simple expression for the excitonic susceptibility (and thus for the dispersion relation) is derived and applied for calculating the field dependence of the transverse excitonic frequency. By an appropriate choice of a certain fitting parameter the calculated energy shift agrees satisfactorily with experimental values obtained recently by Schultheis and Kohler

[en] The existence of a two-parameter set of dressed Langmuir solitons is shown numerically, resolving a discrepancy among earlier investigations

[en] Sulphide, selenide and telluride of lead are narrow gap ionic semiconductors crystallising in the NaCl structure. These compounds have attracted considerable interest during the recent years due to their remarkable dielectric properties. Coherent inelastic scattering of neutrons has provided a wealth of scattering of neutrons has provided us a wealth of data on their phonon dispersion relations. An extensive investigation of the lattice dynamics of these chalcogenides has been presented by employing a different variation of rigid shell model which incorporates the effect of deformation of electron shells as an additional of freedom. The model thus obtained contains the three-body interaction terms as a natural consequence of the regorous theory. The computed phonon frequencies along symmetry directions on most of them are in relatively good agreement with the measured ones, particularly along optical branches, as compaared to the other models. The Debye temperatures variation has also been found to explain the observed data successfully. Thus the inclusion of electron shell diformation effects in the study of the dynamical behaviour of PbS, PbSe and PbTe seems to be quite reasonable. (author)

[en] Using a computer, collisions of oscillating solitons (pulsons) are investigated, their properties depending on space dimension. The results referring to the collision of plane one-dimensional pulsons are described. The properties of motionless cylindrical-symmetrical (CS) pulsons are discussed. The dynamics of their head-on collisions is considered at A=0.4 and at the velocities V₁=-V₂=V=0.2; 0.3; 0.4 and 0.6 (A is the amplitude of field oscillations). Computer calculations show that CS pulsons are stable relative to angular perturbations. At not very small velocities they pass the distance much exceeding their characteristic size. Head-on collision generates strong disturbances of the field function. At the initial velocity V=0.4 pulsons, after mutual overlapping, divide into two dispersing clusters, but then pulsons are spreading out. At less velocities (V=0.2) no division into two clusters is observed. It is noted that conservation of the number of unstable quasiparticles in head-on collisions at V>Vsub(cr) approximately 0.3 is an interesting manifestation of soliton properties

[en] In this paper, we give a coupled lattice equation with the help of Hirota operators, which comes from a special BKP lattice. Two-soliton and three-soliton solutions to the coupled system are constructed. Furthermore, resonant interaction of the two-soliton solution is analyzed in detail. Under some special resonant condition, it is shown that low soliton can propagate faster than high one. Finally, the N-soliton solution is presented in the Pfaffian form. (general)

[en] A complex eigenvalue in the Bogoliubov–de Gennes equations for a stationary Bose-Einstein condensate in the ultracold atomic system indicates the dynamical instability of the system. We also have the modes with zero eigenvalues for the condensate, called the zero modes, which originate from the spontaneous breakdown of symmetries. Although the zero modes are suppressed in many theoretical analyses, we take account of them in this paper and argue that a zero mode can change into one with a pure imaginary eigenvalue by applying a symmetry breaking external perturbation potential. This emergence of a pure imaginary mode adds a new type of scenario of dynamical instability to that characterized by the complex eigenvalue of the usual excitation modes. For illustration, we deal with two one-dimensional homogeneous Bose–Einstein condensate systems with a single dark soliton under a respective perturbation potential, breaking the invariance under translation, to derive pure imaginary modes. - Highlights: • Zero modes are important but ignored in many theories for the cold atomic system. • We discuss the zero mode under symmetry breaking potential in this system. • We consider the zero mode of translational invariance for a single dark soliton. • We show that it turns into an anomalous or pure imaginary mode

[en] We study the dynamics of a high-energy laser pulse in dispersive optical media with large values of self-steepening. We consider the formation of soliton-like peaks at the front of the envelope in such media with anomalous dispersion. We show the possibility of realisation of a medium based on a photonic crystal waveguide with a very large absolute value of the self-steepening parameter in a certain frequency range. (nonlinear optical phenomena)

[en] We investigate localized exciton states in π-conjugated polymers with finite torsion. The localized states are associated with a perturbed transfer integral for which the magnitude of cosine of the torsion angle exceeds the magnitude of the corresponding cosine of the unperturbed system. The localized-state energy and spatial extent are calculated as a function of the ratio of the perturbed to unperturbed transfer integrals. Particular attention is paid to the optically active symmetric localized states, and the effective oscillator strength, or square of the absolute magnitude of the transition dipole moment, is calculated as a function of the energy. The relation of the theory to recent optical studies of poly(di-n-octylfluorene) (PF8) is discussed

[en] We propose a protocol for the simultaneous controlled creation of multiple concentric ring dark solitons in a toroidally trapped flat Bose–Einstein condensate. The decay of these solitons into a vortex–antivortex necklace shows revivals of the soliton structure, but eventually becomes an example of quantum turbulence. (fast track communications)