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Five-component minimum-energy bound states and mobile vector solitons of a spin-orbit-coupled quasi-onedimensional hyperfine-spin-2 Bose-Einstein condensate are studied using the numerical solution and variational approximation of a mean-field model. Two distinct types of solutions with single-peak and multipeak density distribution of the components are identified in different domains of interaction parameters. From an analysis of Galilean invariance and time-reversal symmetry of the Hamiltonian, we establish that vector solitons with multipeak density distribution preserve time-reversal symmetry, but they cannot propagate while maintaining the shape of individual components. However, those with single-peak density distribution violate time-reversal symmetry of the Hamiltonian, but they can propagate with aconstant velocity and maintain the shape of individual components. [ABSTRACT FROM AUTHOR]

We study the ground-state density profile of a spin-orbit-coupled f = 2 spinor condensate in a quasi-onedimensional trap. The Hamiltonian of the system is invariant under time reversal but not under parity. We identify different parity- and time-reversal symmetry-breaking states. The time-reversal symmetry breaking is possible for degenerate states. A phase separation among densities of different components is possible in the domain of time-reversal symmetry breaking. Different types of parity- and time-reversal symmetry-breaking states are predicted analytically and studied numerically. We employ numerical and approximate analytic solutions of a mean-field model in this investigation to illustrate our findings. [ABSTRACT FROM AUTHOR]

We demonstrate stable, robust, bright one-dimensional dipolar Bose-Einstein-condensate (BEC) solitons, moving in a direction perpendicular to the polarization direction, formed due to dipolar interaction for repulsive contact interaction. At medium velocity the head on collision of two such solitons is found to be quasielastic with practically no deformation. Upon small perturbation the solitons are found to exhibit sustained breathing oscillation. The findings are illustrated by numerical simulation using the three-dimensional mean-field Gross-Pitaevskii equation and a reduced two-dimensional model in three and two spatial dimensions employing realistic interaction parameters for a dipolar 164Dy BEC. [ABSTRACT FROM AUTHOR]

We study a spin-orbit (SO)-coupled hyperfine spin-1 Bose-Einstein condensate (BEC) in a quasi-one-dimensional trap. For an SO-coupled BEC in a one-dimensional box, we show that in the absence of the Rabi term, any nonzero value of SO coupling will result in a phase separation among the components for a ferromagnetic BEC, like 87Rb. On the other hand, SO coupling favors miscibility in a polar BEC, like 23Na. In the presence of a harmonic trap, which favors miscibility, a ferromagnetic BEC phase separates, provided that the SO-coupling strength and number of atoms are greater than some critical value. The Rabi term favors miscibility irrespective of the nature of the spin interaction: ferromagnetic or polar. [ABSTRACT FROM AUTHOR]

We demonstrate robust, stable, mobile, quasi-one-dimensional, dark-in-bright dipolar Bose-Einstein-condensate (BEC) solitons with a notch in the central plane formed due to dipolar interaction for repulsive contact interaction. At medium velocity the head-on collision of two such solitons is found to be quasielastic with practically no deformation. A proposal for creating dipolar dark-in-bright solitons in laboratories by phase imprinting is also discussed. A rich variety of such solitons can be formed in dipolar binary BECs, where one can have a dark-in-bright soliton coupled to a bright soliton or two coupled dark-in-bright solitons. The findings are illustrated using numerical simulation in three spatial dimensions by employing realistic interaction parameters for a dipolar 164Dy BEC and a binary 164Dy-162Dy BEC. [ABSTRACT FROM AUTHOR]

We study the Josephson oscillation and self-trapping dynamics of a cigar-shaped dipolar Bose-Einstein condensate of 52Cr atoms polarized along the symmetry axis of an axially symmetric double-well potential using the numerical solution of a mean-field model, for dominating repulsive contact interaction (large positive scattering length a) over an anisotropic dipolar interaction. Josephson-type oscillation emerges for small and very large numbers of atoms, whereas self-trapping is noted for an intermediate number of atoms. The dipolar interaction pushes the system away from self-trapping towards Josephson oscillation. We consider a simple two-mode description for a qualitative understanding of the dynamics. [ABSTRACT FROM AUTHOR]

We demonstrate a fully demixed (separated) robust and stable bright binary dipolar Bose-Einstein-condensate soliton in a quasi-one-dimensional setting formed due to dipolar interactions for repulsive contact interactions. For large repulsive interspecies contact interaction, the first species may spatially separate from the second species, thus, forming a demixed configuration, which can be spatially symmetric or symmetry broken. In the spatially symmetric case, one of the species occupies the central region, whereas, the other species separates into two equal parts and stays predominantly out of this central region. In the symmetry-broken case, the two species stay side by side. Stability phase diagrams for the binary solitons are obtained. The results are illustrated with realistic values of parameters in the binary, 64Dy-l68Er and l64Dy-162Dy mixtures. The demixed solitons are really soliton molecules formed of two types of atoms. A proposal for creating dipolar solitons in experiments is also presented. [ABSTRACT FROM AUTHOR]

We suggest a time-dependent mean-field hydrodynamic model for a binary dipolar boson-fermion mixture to study the stability and collapse of fermions in the 164Dy-161Dy mixture. The condition of stability of the dipolar mixture is illustrated in terms of phase diagrams. A collapse is induced in a disk-shaped stable binary mixture by jumping the interspecies contact interaction from repulsive to attractive by the Feshbach resonance technique. The subsequent dynamics is studied by solving the time-dependent mean-field model including three-body loss due to molecule formation in boson-fermion and boson-boson channels. Collapse and fragmentation in the fermions after subsequent explosions are illustrated. The anisotropic dipolar interaction leads to anisotropic fermionic density distribution during collapse. This study is carried out in three-dimensional space using realistic values of dipolar and contact interactions. [ABSTRACT FROM AUTHOR]

We study the statics and dynamics of a dipolar Bose-Einstein condensate (BEC) droplet bound by interspecies contact interaction in a trapped nondipolar BEC. Our findings are demonstrated in terms of stability plots of a dipolar 164Dy droplet bound in a trapped nondipolar 87Rb BEC with a variable number of 164Dy atoms and interspecies scattering length. A trapped nondipolar BEC of a fixed number of atoms can bind only a dipolar droplet containing fewer atoms than a critical number for the interspecies scattering length between two critical values. The shape and size (statics) as well as the small breathing oscillation (dynamics) of the dipolar BEC droplet are studied using numerical and variational solutions of a mean-field model. We also suggest an experimental procedure for achieving such a 164Dy droplet by relaxing the trap on the 164Dy BEC in a trapped binary 87Rb-,164Dy mixture. [ABSTRACT FROM AUTHOR]

We study the static properties of disk-shaped binary dipolar Bose-Einstein condensates of 168Er-164Dy and 52Cr-164Dy mixtures under the action of interspecies and intraspecies contact and dipolar interactions and demonstrate the effect of dipolar interaction using the mean-field approach. Throughout this study we use realistic values of interspecis and intraspecies dipolar interactions and the intraspecies scattering lengths and consider the interspecies scattering length as a parameter. The stability of the binary mixture is illustrated through phase plots involving a number of atoms of the species. The binary system always becomes unstable as the number of atoms increases beyond a certain limit. As the interspecies scattering length increases corresponding to more repulsion, an overlapping mixed state of the two species changes to a separated demixed configuration. During the transition from a mixed to a demixed configuration as the interspecies scattering length is increased for parameters near the stability line, the binary condensate shows special transient structures in density in the form of red-blood-cell-like biconcave and Saturn-ring-like shapes, which are direct manifestations of the dipolar interaction. [ABSTRACT FROM AUTHOR]

We study properties of a trapped dipolar Bose-Einstein condensate (BEC) in a circular ring or a spherical shell using the mean-field Gross-Pitaevskii equation. In the case of the ring-shaped trap we consider different orientations of the ring with respect to the polarization direction of the dipoles. In the presence of long-range anisotropic dipolar and short-range contact interactions, the anisotropic density distribution of the dipolar BEC in both traps is discussed in detail. The stability condition of the dipolar BEC in both traps is illustrated in a phase plot of dipolar and contact interactions. We also study and discuss the properties of a vortex dipolar BEC in these traps. [ABSTRACT FROM AUTHOR]

A uniform dilute Bose gas of known density has a universal behavior as the atomic scattering length tends to infinity at unitarity while most of its properties are determined by a universal parameter £ relating the energies of the noninteracting and unitary gases. The usual mean-field equation is not valid in this limit, and beyond mean-field corrections become important. We use a dynamical model including such corrections to investigate a trapped disk-shaped dipolar Bose-Einstein condensate (BEC) and a dipolar BEC vortex for large scattering length. We study the sensitivity of our results on the parameter f and discuss the possibility of extracting the value of this parameter from experimental observables. [ABSTRACT FROM AUTHOR]

By numerical solution and variational approximation of the Gross-Pitaevskii equation, we studied the localization of a noninteracting and weakly interacting Bose-Einstein condensate in a weakly perturbed optical lattice in one and three dimensions. The perturbation achieved through a weak delocalizing expulsive or a linear potential as well as a weak localizing harmonic potential removes the periodicity of the optical lattice and leads to localization. We also studied some dynamics of the localized state confirming its stability. [ABSTRACT FROM AUTHOR]

We study the localization of a cigar-shaped superfluid Bose-Fermi mixture in a quasiperiodic bichromatic optical lattice (OL) for interspecies attraction and intraspecies repulsion. The mixture is described by the Gross-Pitaevskii equation for the bosons, coupled to a hydrodynamic mean-field equation for fermions at unitarity. We confirm the existence of the symbiotic localized states in the Bose-Fermi mixture and Anderson localization of the Bose component in the interacting Bose-Fermi mixture on a bichromatic OL. The phase diagram in boson and fermion numbers showing the regions of the symbiotic and Anderson localization of the Bose component is presented. Finally, the stability of symbiotic and Anderson localized states is established under small perturbations. [ABSTRACT FROM AUTHOR]

By direct numerical simulation and variational solution of the Gross-Pitaevskii equation, we studied the stationary and dynamic characteristics of a cigar-shaped, localized, collisionally inhomogeneous Bose-Einstein condensate trapped in a one-dimensional bichromatic quasiperiodic optical-lattice potential, as used in a recent experiment on the localization of a Bose-Einstein condensate [ Roati et al. Nature (London) 453 895 (2008)]. The effective potential characterizing the spatially modulated nonlinearity is obtained. It is found that the collisional inhomogeneity has influence not only on the central region but also on the tail of the Bose-Einstein condensate. The influence depends on the sign and value of the spatially modulated nonlinearity coefficient. We also demonstrate the stability of the stationary localized state by performing a standard linear stability analysis. Where possible, the numerical results are shown to be in good agreement with the variational results. [ABSTRACT FROM AUTHOR]

Wave equations in an anisotropic plasma imbedded in a moving dielectric medium have been derived through Maxwell-Minkowski relations. These are solved for longitudinal and transverse cases of propagation. The dispersion relation within the medium has been deduced through which the nature of splitting may be understood.

Generation of short-range gravity waves within the ionosphere due to inhomogenous heating in the presence of space-localized inhomogeneities during high-power radio wave-propagation has been investigated. The magnitude and from of the anticipated atmospheric wave-trains are obtained. The derived experession of electric field within the ionosphere under the stated perturbed condition may be considered to be manifested through Lorentz-force and Joule-dissipation that influence the neutral gas of the atmosphere via collision-mechanism and thereby gravity waves are launched. The expressions for the low-frequency part of the fractional pressure variations have been derived which are applied to theE-region of the ionosphere. The results are presented graphically.

A brief review of Čerenkov radiation within the upper atmospheric plasma has been presented. Different attempts in this context are systematically discussed. The results of analysis about the nature and characteristics of VLF hisses in terms of incoherent Čerenkov radiation are given in a concise manner. The occurrence of resonance cone has also been reported.

An expression for the susceptibility dyadic appropriate to the lower regions of the atmospheric plasma is derived using Maxwell's field equations and the equation of conservation of momentum. The contributions due to viscous effect and convection current density are incorporated in the physical processes within the stated medium. Utilizing the approximation of linearized equations, second order coupled wave equations have been derived through the dyadic.

Enhancement of conductivity tensor modification within the ionospheric plasma by electron density modulation through the temperature dependence of the recombination rates of different ionspecies caused due to electron temperature modulation during high-power wave propagation is studied. Variation of Hall and Pedersen conductivities of the ionosphere has been investigated in the height range between 85 km to 250 km. The generation of waves at the modulation frequency and its harmonics in the ELF, VLF bands in the process is discussed.

Magnetohydrodynamic formulation has been used to deduce the velocity distribution of the upper atmospheric movement caused by the auroral electric field at the thermospheric height. The expressions for Joule heating and viscous heating are obtained. Numerical analysis has been made to estimate their magnitudes as well as the rate of their variations with time. The results are presented graphically.

Coupled equations are derived for different ionospheric parameters through susceptibility dyadic appropriate to the medium. The nature of dispersion within the medium is studied.

Some anomalous TV receptions in India on band I have been interpreted as being propagated viaF-layer artificially modified by high power broadcast transmitters. In this paper, the possibility of VHF communication by artificially modifiedE-layer is discussed. The presented theoretical analysis shows that high-power broadcast trasmitters can produce substantial changes in temperature and ionisation in theE-layer. The rate of energy transfer from the wave to the medium particles has also been computed. Model calculations are made for a transmitter located near Calcutta. The possibility of the extra-ionisation producing field-aligned structures to support VHF communication is discussed.

The gradient coupling within the ionospheric plasma in the presence of local variation of atmospheric heating and other modifications during high power radio wave propagation has been studied. The appropriate form of coupled equations for the modified situation is obtained. The electromagnetic and acoustic modes of wave propagation have been separated and solved, by the WKB method. Field quantities may be used to explore different properties of the medium under the modified condition.

The non-linear heating of electrons in the ionospheric plasma due to high-power radio wave propagation has been investigated through an integro-differential equation derived from Boltzmann velocity-moment equations. Various processes appropriate to the situation under study are taken into account. The numerical solution of the derived equation is presented graphically.

We study the statics and dynamics of a stable, mobile, three-dimensional matter-wave spherical quantum ball created in the presence of an attractive two-body and a very small repulsive three-body interaction. The quantum ball can propagate with a constant velocity in any direction in free space and its stability under a small perturbation is established numerically and variationally. In frontal head-on and angular collisions at large velocities two quantum balls behave like quantum solitons. Such collision is found to be quasielastic and the quantum balls emerge after collision without any change of direction of motion and velocity and with practically no deformation in shape. When reflected by a hard impenetrable plane, the quantum ball bounces off like a wave obeying the law of reflection without any change of shape or speed. However, in a collision at small velocities two quantum balls coalesce to form a larger ball which we call a quantum-ball breather. We point out the similarity and difference between the collision of two quantum and classical balls. The present study is based on an analytic variational approximation and a full numerical solution of the mean-field Gross-Pitaevskii equation using the parameters of 7Li atoms. [ABSTRACT FROM AUTHOR]

We study the vortex-bright solitons in a quasi-two-dimensional spin-orbit-coupled (SO-coupled) hyperfine spin-1 three-component Bose-Einstein condensate using variational method and numerical solution of a mean-field model. The ground state of these vortex-bright solitons is radially symmetric for weak ferromagnetic and polar interactions. For a sufficiently strong ferromagnetic interaction, we observe the emergence of an asymmetric vortex-bright soliton as the ground state. We also numerically investigate stable moving solitons and binary collision between them. The present mean-field model is not Galilean invariant, and we use a Galilean-transformed model for generating the moving solitons. At low velocities, the head-on collision between two in-phase solitons results either in collapse or fusion of the soliton pair. On the other hand, in head-on collision, the two out-of-phase solitons strongly repel each other and trace back their trajectories before the actual collision. At low velocities, in a collision with an impact parameter, the out-of-phase solitons get deflected from their original trajectory like two rigid classical disks. These out-of-phase solitons behave like classical disks, and their collision dynamics is governed by classical laws of motion. However, at large velocities two SO-coupled spinor solitons, irrespective of phase difference, can pass through each other in a head-on collision like two quantum solitons. [ABSTRACT FROM AUTHOR]

We classify all possible fractional charge vortices of charge less than unity in spin-1 and spin-2 polar and cyclic Bose-Einstein condensates (BECs) with zero magnetization. Statics and dynamics of these vortices in quasi-two-dimensional spinor BECs are studied employing an accurate numerical solution and a Lagrange variational approximation. The results for density and collective-mode oscillation are illustrated using the fractional-charge BEC vortex of 23Na and 87Rb atoms with realistic interaction and trapping potential parameters. [ABSTRACT FROM AUTHOR]

We study the localization of a noninteracting and weakly interacting Bose-Einstein condensate (BEC) with spin-orbit coupling loaded in a quasiperiodic bichromatic optical lattice potential using the numerical solution and variational approximation of a binary mean-field Gross-Pitaevskii equation with two pseudospin components. We confirm the existence of the stationary localized states in the presence of the spin-orbit and Rabi couplings for an equal distribution of atoms in the two components. We find that the interaction between the spin-orbit and Rabi couplings favors the localization or derealization of the BEC depending on the phase difference between the components. We also studied the oscillation dynamics of the localized states for an initial population imbalance between the two components. [ABSTRACT FROM AUTHOR]

A close coupling quantum-mechanical calculation is performed for rotational energy transfer in a HD + HD collision at very low energy, down to the ultracold temperatures: T ∼ 10-8 K. A global six-dimensional H2-H2 potential-energy surface is adopted from a previous work [Boothroyd et ai, J. Chem. Phys. 116, 666 (2002)]. State-resolved integral cross sections &sgr;ij→i′j′(&egr;kim) of different quantum-mechanical rotational transitions ij→i′j′ in the HD molecules and corresponding state-resolved thermal rate coefficients kij→i′j′(T) have been computed. Additionally, for comparison, H2 + H2 calculations for a few selected rotational transitions have also been performed. The hydrogen and deuterated hydrogen molecules are treated as rigid rotors in this work. A pronounced isotope effect is identified in the cross sections of these collisions at low and ultracold temperatures [ABSTRACT FROM AUTHOR]