Dissipation-managed soliton in a quasi-one-dimensional Bose-Einstein condensate

We use the time-dependent mean-field Gross-Pitaevskii equation to study the formation of a dynamically-stabilized dissipation-managed bright soliton in a quasi-one-dimensional Bose-Einstein condensate (BEC). Because of three-body recombination of bosonic atoms to molecules, atoms are lost (dissipated) from a BEC. Such dissipation leads to the decay of a BEC soliton. We demonstrate by a perturbation procedure that an alimentation of atoms from an external source to the BEC may compensate for the dissipation loss and lead to a dynamically-stabilized soliton. The result of the analytical perturbation method is in excellent agreement with mean-field numerics. It seems possible to obtain such a dynamically-stabilized BEC soliton without dissipation in laboratory.Comment: 5 pages, 3 figure

Limits of validity for a semiclassical mean-field two-fluid model for Bose-Einstein condensation thermodynamics

We reinvestigate the Bose-Einstein condensation (BEC) thermodynamics of a weakly interacting dilute Bose gas under the action of a trap using a semiclassical two-fluid mean-field model in order to find the domain of applicability of the model. Such a model is expected to break down once the condition of diluteness and weak interaction is violated. We find that this breakdown happens for values of coupling and density near the present experimental scenario of BEC. With the increase of the interaction coupling and density the model may lead to unphysical results for thermodynamic observables.Comment: Five latex pages, four postscript figures, Accepted in Physica

Coordinate-space Faddeev-Hahn-type approach to three-body charge transfer reactions involving exotic particles

Low-energy muon-transfer cross sections and rates in collisions of muonic atoms with hydrogen isotopes are calculated using a six-state close-coupling approximation to coordinate-space Faddeev-Hahn-type equations. In the muonic case satisfactory results are obtained for all hydrogen isotopes and the experimentaly observed strong isotopic dependence of transfer rates is also reproduced. A comparison with results of other theoretical and available experimental works is presented. The present model also leads to good transfer cross sections in the well-understood problem of antihydrogen formation in antiproton-positronium collision.Comment: 18 pages REVTeX, accepted for publication in Phys. Rev.

Universal scaling in BCS superconductivity in two dimensions in non-s waves

The solutions of a renormalized BCS model are studied in two space dimensions in $s$, $p$ and $d$ waves for finite-range separable potentials. The gap parameter, the critical temperature $T_c$, the coherence length $\xi$ and the jump in specific heat at $T_c$ as a function of zero-temperature condensation energy exhibit universal scalings. In the weak-coupling limit, the present model yields a small $\xi$ and large $T_c$ appropriate to those for high-$T_c$ cuprates. The specific heat, penetration depth and thermal conductivity as a function of temperature show universal scaling in $p$ and $d$ waves.Comment: 11 pages, LATEX, 4 postscript figures embedded using eps

Perpendicular magnetic anisotropy in bulk and thin-film CuMnAs for antiferromagnetic memory applications

CuMnAs with perpendicular magnetic anisotropy is proposed as an active material for antiferromagnetic memory. Information can be stored in the antiferromagnetic domain state, while writing and readout can rely on the existence of the surface magnetization. It is predicted, based on first-principles calculations, that easy-axis anisotropy can be achieved in bulk CuMnAs by substituting a few percent of As atoms by Ge, Si, Al, or B. This effect is attributed to the changing occupation of certain electronic bands near the Fermi level induced by the hole doping. The calculated temperature dependence of the magnetic anisotropy does not exhibit any anomalies. Thin CuMnAs(001) films are also predicted to have perpendicular magnetic anisotropy.Comment: 5 pages, 8 figure

Spatial Patterns of Urban Growth - Does Location Matter? a Case Study of Nepal

Between 1952 and 2001, the number of urban settlements in Nepal grew from 10 to 58, while their share in the country’s population increased from 2.6 to 14.4%. However, the spatial distribution of urban growth was uneven. The fastest growing urban localities are situated near major population centers, close to highways, and in the vicinity of the In-dian border. Urban localities elsewhere exhibited sluggish economic growth and poor socio-demographic performance. Data for this analysis were drawn from databases maintained by Nepal’s Central Bureau of Statistics; the Municipalities’ Association; the Ministry of Local Development and its Department of Topographical Survey. In the GIS-assisted analysis, spatial reference data (e.g., distances between individual municipalities and major rivers, roads, international borders and major population centers) were matched against five performance indexes, viz. annual population growth, per capita in-come and expenditures of local municipalities, telephone ownership, number of primary schools, and number of industries.