6,567 research outputs found
Collective modes of a harmonically trapped one-dimensional Bose gas: the effects of finite particle number and nonzero temperature
Following the idea of the density functional approach, we develop a
generalized Bogoliubov theory of an interacting Bose gas confined in a
one-dimensional harmonic trap, by using a local chemical potential - calculated
with the Lieb-Liniger exact solution - as the exchange energy. At zero
temperature, we use the theory to describe collective modes of a
finite-particle system in all interaction regimes from the ideal gas limit, to
the mean-field Thomas-Fermi regime, and to the strongly interacting
Tonks-Girardeau regime. At finite temperature, we investigate the temperature
dependence of collective modes in the weak-coupling regime by means of a
Hartree-Fock-Bogoliubov theory with Popov approximation. By emphasizing the
effects of finite particle number and nonzero temperature on collective mode
frequencies, we make comparisons of our results with the recent experimental
measurement [E. Haller et al., Science 325, 1224 (2009)] and some previous
theoretical predictions. We show that the experimental data are still not fully
explained within current theoretical framework.Comment: 10 pages, 8 figure
Emergent Dark Matter in Late Time Universe on Holographic Screen
We discuss a scenario that the dark matter in late time universe emerges as
part of the holographic stress-energy tensor on the hypersurface in higher
dimensional flat spacetime. Firstly we construct a toy model with a de Sitter
hypersurface as the holographic screen in the flat bulk. After adding the
baryonic matter on the screen, we assume that both of the dark matter and dark
energy can be described by the Brown-York stress-energy tensor. From the
Hamiltonian constraint equation in the flat bulk, we find an interesting
relation between the dark matter and baryonic matter's energy density
parameters, by comparing with the Lambda cold dark matter parameterization. We
further compare this holographic embedding of emergent dark matter with
traditional braneworld scenario and present an alternative interpretation as
the holographic universe. It can be reduced to our toy constraint in the late
time universe, with the new parameterization of the Friedmann equation. We also
comment on the possible connection with Verlinde's emergent gravity, where the
dark matter is treated as the elastic response of the baryonic matter on the de
Sitter spacetime background. We show that from the holographic de Sitter model
with elasticity, the Tully-Fisher relation and the dark matter distribution in
the galaxy scale can be derived.Comment: 28 pages, 2 figures; Matches published version and we thank the
referees for many insightful comments; v3: typos in the Friedmann equations
are fixe
Bell Inequality in the Holographic EPR Pair
We study the Bell inequality in a holographic model of the casually
disconnected Einstein-Podolsky-Rosen (EPR) pair. The
Clauser-Horne-Shimony-Holt(CHSH) form of Bell inequality is constructed using
holographic Schwinger-Keldysh (SK) correlators. We show that the manifestation
of quantum correlation in Bell inequality can be holographically reproduced
from the classical fluctuations of dual accelerating string in the bulk
gravity. The violation of this holographic Bell inequality supports the
essential quantum property of this holographic model of an EPR pair.Comment: 8 pages, 2 figures; references and texts added; v3: matches published
versio
Petrov type I Condition and Rindler Fluid in Vacuum Einstein-Gauss-Bonnet Gravity
Recently the Petrov type I condition is introduced to reduce the degrees of
freedom in the extrinsic curvature of a timelike hypersurface to the degrees of
freedom in the dual Rindler fluid in Einstein gravity. In this paper we show
that the Petrov type I condition holds for the solutions of vacuum
Einstein-Gauss-Bonnet gravity up to the second order in the relativistic
hydrodynamic expansion. On the other hand, if imposing the Petrov type I
condition and Hamiltonian constraint on a finite cutoff hypersurface, the
stress tensor of the relativistic Rindler fluid in vacuum Einstein-Gauss-Bonnet
gravity can be recovered with correct first order and second order transport
coefficients.Comment: 25 page
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