9,626 research outputs found
Supercurrent Stability in a Quasi-1D Weakly Interacting Bose Gas
We discuss a possibility of observing superfluid phenomena in a quasi-1D
weakly interacting Bose gas at finite temperatures. The weakness of interaction
in combination with generic properties of 1D liquids can result in a situation
when relaxational time of supercurrent is essentially larger than the time of
experimental observation, and the behavior of the system is indistinguishable
from that of a genuine superfluid.Comment: Revtex, 4 pages, no figures; Submitted to Phys. Rev. A (Brief
Reports
Critical Dynamics of a Two-dimensional Superfluid near a Non-Thermal Fixed Point
Critical dynamics of an ultracold Bose gas far from equilibrium is studied in
two spatial dimensions. Superfluid turbulence is created by quenching the
equilibrium state close to zero temperature. Instead of immediately
re-thermalizing, the system approaches a meta-stable transient state,
characterized as a non-thermal fixed point. A focus is set on the vortex
density and vortex-antivortex correlations which characterize the evolution
towards the non-thermal fixed point and the departure to final
(quasi-)condensation. Two distinct power-law regimes in the vortex-density
decay are found and discussed in terms of a vortex binding-unbinding transition
and a kinetic description of vortex scattering. A possible relation to decaying
turbulence in classical fluids is pointed out. By comparing the results to
equilibrium studies of a two-dimensional Bose gas, an intuitive understanding
of the location of the non-thermal fixed point in a reduced phase space is
developed.Comment: 11 pages, 13 figures; PRA versio
Market Power in Non-Metro Banking
Banks in non-metropolitan areas compete in a spatially-differentiated environment. This paper estimates a structural model of the supply and demand of banking services in which pricing power depends on the distance between rival banks. A spatial econometric model finds that approximately 38.0% of economic surplus derives from spatial market power.Financial Economics,
Profitability and Long-term Survival of Community Banks: Evidence from Texas
This study examines the impact of distance among competing bank locations on market their pricing behavior. A general spatial autoregressive model that nests both spatial autoregressive and spatial error models is used to examine the impact of distance on pricing behavior of 686 non-metro banks in Texas. Results show that non-metro banks exercise market power in pricing their products. An increase in spatial competition may reduce profitability and challenge long term survival of small community based financial institutions.Financial Economics,
Enhanced Dimer Relaxation in an Atomic/Molecular BEC
We derive a universal formula for the rate constant \beta for relaxation of a
shallow dimer into deeply-bound diatomic molecules in the case of atoms with a
large scattering length a. We show that \beta is determined by a and by two
3-body parameters that also determine the binding energies and widths of Efimov
states. The rate constant \beta scales like \hbar a/m near the resonance, but
the coefficient is a periodic function of ln(a) that may have resonant
enhancement at values of a that differ by multiples of 22.7.Comment: 5 pages, revtex4, 2 PS figures, title changed, final versio
Universal low-energy properties of three two-dimensional particles
Universal low-energy properties are studied for three identical bosons
confined in two dimensions. The short-range pair-wise interaction in the
low-energy limit is described by means of the boundary condition model. The
wave function is expanded in a set of eigenfunctions on the hypersphere and the
system of hyper-radial equations is used to obtain analytical and numerical
results. Within the framework of this method, exact analytical expressions are
derived for the eigenpotentials and the coupling terms of hyper-radial
equations. The derivation of the coupling terms is generally applicable to a
variety of three-body problems provided the interaction is described by the
boundary condition model. The asymptotic form of the total wave function at a
small and a large hyper-radius is studied and the universal logarithmic
dependence in the vicinity of the triple-collision point is
derived. Precise three-body binding energies and the scattering length
are calculated.Comment: 30 pages with 13 figure
Does Internet Banking Affect the Performance of Community Banks?
This study examines the impact of online banking on bank performance. Results show that online banking improves bank earnings as well as helps in improving asset quality.Research and Development/Tech Change/Emerging Technologies,
Finite temperature correlations and density profiles of an inhomogeneous interacting 1D Bose gas
We calculate the density profiles and density correlation functions of the
one-dimensional Bose gas in a harmonic trap, using the exact finite-temperature
solutions for the uniform case, and applying a local density approximation. The
results are valid for a trapping potential which is slowly varying relative to
a correlation length. They allow a direct experimental test of the transition
from the weak coupling Gross-Pitaevskii regime to the strong coupling,
'fermionic' Tonks-Girardeau regime. We also calculate the average two-particle
correlation which characterizes the bulk properties of the sample, and find
that it can be well approximated by the value of the local pair correlation in
the trap center.Comment: Final published version; updated references; 19 pages, 12 figure
Spatial Correlation Functions of one-dimensional Bose gases at Equilibrium
The dependence of the three lowest order spatial correlation functions of a
harmonically confined Bose gas on temperature and interaction strength is
presented at equilibrium. Our analysis is based on a stochastic Langevin
equation for the order parameter of a weakly-interacting gas. Comparison of the
predicted first order correlation functions to those of appropriate mean field
theories demonstrates the potentially crucial role of density fluctuations on
the equilibrium coherence length. Furthermore,the change in both coherence
length and shape of the correlation function, from gaussian to exponential,
with increasing temperature is quantified. Moreover, the presented results for
higher order correlation functions are shown to be in agreeement with existing
predictions. Appropriate consideration of density-density correlations is shown
to facilitate a precise determination of quasi-condensate density profiles,
providing an alternative approach to the bimodal density fits typically used
experimentally
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