1,703 research outputs found
Condensate density and superfluid mass density of a dilute Bose gas near the condensation transition
We derive, through analysis of the structure of diagrammatic perturbation
theory, the scaling behavior of the condensate and superfluid mass density of a
dilute Bose gas just below the condensation transition. Sufficiently below the
critical temperature, , the system is governed by the mean field
(Bogoliubov) description of the particle excitations. Close to , however,
mean field breaks down and the system undergoes a second order phase
transition, rather than the first order transition predicted in Bogoliubov
theory. Both condensation and superfluidity occur at the same critical
temperature, and have similar scaling functions below , but
different finite size scaling at to leading order in the system size.
Through a simple self-consistent two loop calculation we derive the critical
exponent for the condensate fraction, .Comment: 4 page
Strong Interaction Dynamics from Spontaneous Symmetry Breaking of Scale Invariance
Using the mechanism of spontaneous symmetry breaking of scale invariance
obtained from the dynamics of maximal rank field strengths, it is possible to
spontaneously generate confining behavior. Introducing a dilaton field, the
study of non trivial confining and de-confining transitions appears possible.
This is manifest in two ways at least: One can consider bags which contain an
unconfined phase in the internal region and a confined phase outside and also
one obtains a simple model for deconfinement at high Temperature from the
finite Temperature dynamics of the dilaton field.Comment: Latex, 5 pages, references added, few typos corrected and more
consistent notation introduced. Final version to appear in Mod. Phys. Lett.
Color, Spin and Flavor Diffusion in Quark-Gluon Plasmas
In weakly interacting quark-gluon plasmas diffusion of color is found to be
much slower than the diffusion of spin and flavor because color is easily
exchanged by the gluons in the very singular forward scattering processes. If
the infrared divergence is cut off by a magnetic mass, ,
the color diffusion is , a
factor smaller than spin and flavor diffusion. A similar effect is
expected in electroweak plasmas above due to exchanges. The color
conductivity in quark-gluon plasmas and the electrical conductivity in
electroweak plasmas are correspondingly small in relativistic heavy ion
collisions and the very early universe.Comment: 5 pages, no figure
Hadron-quark continuity induced by the axial anomaly in dense QCD
We investigate the interplay between the chiral and diquark condensates on
the basis of the Ginzburg-Landau potential with QCD symmetry. We demonstrate
that the axial anomaly drives a new critical point at low temperature in the
QCD phase diagram and leads to a smooth crossover between the hadronic and
color superconducting phases.Comment: 4 pages, 5 figures, to appear in the Proceedings of Quark Matter 2006
held in Shangha
Low Energy Dynamics in Ultradegenerate QCD Matter
We study the low energy behavior of QCD Green functions in the limit that the
baryon chemical potential is much larger than the QCD scale parameter
. We show that there is a systematic low energy expansion in
powers of , where is the energy and is the
screening scale. This expansion is valid even if the effective quark-gluon
coupling is not small. The expansion is purely perturbative in the magnetic
regime . If the external momenta and energies satisfy , planar, abelian ladder diagrams involving the full quark
propagator have to be resummed but the corresponding Dyson-Schwinger equations
are closed.Comment: 4 pages, published versio
Peierls substitution in the energy dispersion of a hexagonal lattice
The method of the Peierls substitution in studying the magnetic subband
structure of a hexagonal lattice is re-examined. Several errors in the
formalism of a couple of recent papers are pointed out and rectified so as to
describe the effect of the magnetic field pertinently.Comment: 3 pages (two-columns), 2 EPS figures, submitted to J. Phys.: Condens.
Matte
Velocity of vortices in inhomogeneous Bose-Einstein condensates
We derive, from the Gross-Pitaevskii equation, an exact expression for the
velocity of any vortex in a Bose-Einstein condensate, in equilibrium or not, in
terms of the condensate wave function at the center of the vortex. In general,
the vortex velocity is a sum of the local superfluid velocity, plus a
correction related to the density gradient near the vortex. A consequence is
that in rapidly rotating harmonically trapped Bose-Einstein condensates, unlike
in the usual situation in slowly rotating condensates and in hydrodynamics,
vortices do not move with the local fluid velocity. We indicate how Kelvin's
conservation of circulation theorem is compatible with the velocity of the
vortex center being different from the local fluid velocity. Finally we derive
an exact wave function for a single vortex near the rotation axis in a weakly
interacting system, from which we derive the vortex precession rate.Comment: 5 pages, one .eps figure. Published versio
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