215,052 research outputs found
The angular momentum of a magnetically trapped atomic condensate
For an atomic condensate in an axially symmetric magnetic trap, the sum of
the axial components of the orbital angular momentum and the hyperfine spin is
conserved. Inside an Ioffe-Pritchard trap (IPT) whose magnetic field (B-field)
is not axially symmetric, the difference of the two becomes surprisingly
conserved. In this paper we investigate the relationship between the values of
the sum/difference angular momentums for an atomic condensate inside a magnetic
trap and the associated gauge potential induced by the adiabatic approximation.
Our result provides significant new insight into the vorticity of magnetically
trapped atomic quantum gases.Comment: 4 pages, 1 figure
Laser-catalyzed spin-exchange process in a Bose-Einstein condensate
We show theoretically that it is possible to optically control collective
spin-exchange processes in spinor Bose condensates through virtual
photoassociation. The interplay between optically induced spin exchange and
spin-dependent collisions provides a flexible tool for the control of atomic
spin dynamics, including enhanced or inhibited quantum spin oscillations, the
optically-induced ferromagnetic-to-antiferromagnetic transition, and coherent
matter-wave spin conversion.Comment: 4 pages, 4 figure
Long-Ranged Orientational Order in Dipolar Fluids
Recently Groh and Dietrich claimed the thermodynamic state of a dipolar fluid
depends on the shape of the fluid's container. For example, a homogeneous fluid
in a short fat container would phase separate when transferred to a tall skinny
container of identical volume and temperature. Their calculation thus lacks a
thermodynamic limit. We show that removal of demagnetizing fields restores the
true, shape independent, thermodynamic limit. As a consequence, spontaneously
magnetized liquids display inhomogeneous magnetization textures.Comment: 3 pages, LaTex, no figures. Submitted as comment to PRL, May 199
Precision era of the kinetic Sunyaev-Zeldovich effect: simulations, analytical models and observations and the power to constrain reionization
The kinetic SZ effect, which is the dominant CMB source at arc-minute scales
and Ghz, probes the ionized gas peculiar momentum up to the
epoch of reionization and is a sensitive measure of the reionization history.
We ran high resolution self-similar and CDM hydro simulations and
built an analytical model to study this effect. Our model reproduces the
CDM simulation results to several percent accuracy, passes various
tests against self-similar simulations, and shows a wider range of
applicability than previous analytical models. Our model in its continuous
version is free of simulation limitations such as finite simulation box and
finite resolution and allows an accurate prediction of the kinetic SZ power
spectrum . For the WMAP cosmology, we find for the reionization redshift and
. The corresponding temperature fluctuation is several K at
these ranges. The dependence of on the reionization history allows an
accurate measurement of the reionization epoch. For the Atacama cosmology
telescope experiment, can be measured with accuracy.
scales as . Given cosmological parameters,
ACT would be able to constrain with several percent accuracy.
Some multi-reionization scenarios degenerate in the primary CMB temperature and
TE measurement can be distinguished with confidence.Comment: 14 pages, 7 figures. Accepted by MNRAS. We corrected the primary CMB
power spectrum we used. We added discussions about the effects of lensing and
relativistic SZ correctio. We withdraw a claim about the patchy reionizatio
Massive particles' Hawking radiation via tunneling from the G.H Dilaton black hole
In the past, Hawking radiation was viewed as a tunneling process and the
barrier was just created by the outgoing particle itself. In this paper,
Parikh's recent work is extended to the case of massive particles' tunneling.
We investigate the behavior of the tunneling massive particles from a
particular black hole solution-G.H Dilaton black hole which is obtained from
the string theory, and calculate the emission rate at which massive particles
tunnel across the event horizon. We obtain that the result is also consistent
with an underlying unitary theory. Furthermore, the result takes the same
functional form as that of massless particles.Comment: 6 pages, no figure, revtex
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