72,985 research outputs found
Ground state and vortex states of bosons in an anisotropic trap: A variational approach
We propose a simple variational form of the wave function to describe the
ground state and vortex states of a system of weakly interacting Bose gas in an
anisotropic trap. The proposed wave function is valid for a wide range of the
particle numbers in the trap. It also works well in the case of attractive
interaction between the atoms. Further, it provides an easy and fast method to
calculate the physical quantities of interest. The results compare very well
with those obtained by purely numerical techniques. Using our wave function we
have been able to verify, for the first time, the predicted behaviour of aspect
ratio.Comment: Revised version, To appear in the special issue of European Physical
Journal
Crystallization of Simple Fluids: Relative Stability of f.c.c. and b.c.c Structures
A free-energy functional for a crystal that contains both the symmetry
conserved and symmetry broken parts of the direct pair correlation function is
developed. The free-energy functional is used to investigate the
crystallization of fluids interacting via the inverse power potential ;
. In agreement with simulation results we find
that for the freezing is into close packed f.c.c structure while for
soft repulsions b.c.c phase is more stable.Comment: 9 pages, 2 figure
Cosmic Evolution in Generalised Brans-Dicke Theory
We have studied the Generalised Brans-Dicke theory and obtained exact
solutions of a(t),phi(t),and omega(t) for different epochs of the cosmic
evolution .We discuss how inflation,decceleration,cosmic acceleration can
result from this solution.The time variation of G(t) is also examined.Comment: 12 pages, no figure
ATTac-2000: An Adaptive Autonomous Bidding Agent
The First Trading Agent Competition (TAC) was held from June 22nd to July
8th, 2000. TAC was designed to create a benchmark problem in the complex domain
of e-marketplaces and to motivate researchers to apply unique approaches to a
common task. This article describes ATTac-2000, the first-place finisher in
TAC. ATTac-2000 uses a principled bidding strategy that includes several
elements of adaptivity. In addition to the success at the competition, isolated
empirical results are presented indicating the robustness and effectiveness of
ATTac-2000's adaptive strategy
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