23,041 research outputs found
Three-loop HTL QCD thermodynamics
The hard-thermal-loop perturbation theory (HTLpt) framework is used to
calculate the thermodynamic functions of a quark-gluon plasma to three-loop
order. This is the highest order accessible by finite temperature perturbation
theory applied to a non-Abelian gauge theory before the high-temperature
infrared catastrophe. All ultraviolet divergences are eliminated by
renormalization of the vacuum, the HTL mass parameters, and the strong coupling
constant. After choosing a prescription for the mass parameters, the three-loop
results for the pressure and trace anomaly are found to be in very good
agreement with recent lattice data down to , which are
temperatures accessible by current and forthcoming heavy-ion collision
experiments.Comment: 27 pages, 11 figures; corresponds with published version in JHE
Gas Rich Dwarfs from the PSS-II III. HI Profiles and Dynamical Masses
We present Arecibo neutral hydrogen data on a sample of optically selected
dwarf galaxies. The sample ranges in HI mass from 10^6 M_sun to 5x10^9 M_sun,
with a mean of 7.9x10^8 M_sun. Using estimated HI radii, the HI surface
densities range from 0.6 to 20 M_sun pc^-2, all well below the critical
threshold for star formation (Kennicutt 1998). M_HI/L values of the LSB dwarfs
range from 0.3 to 12 with a mean value of 2.0. Dynamical masses, calculated
from the HI profile widths, range from 10^8 M_sun to 10^11 M_sun. There is a
strong correlation between optical luminosity and dynamical mass for LSB dwarfs
implying that the dark matter (whether baryonic or non-baryonic) follows the
detectable baryonic matter.Comment: 53 pages, AASTeX v4.0, 8 figures, to be published in ApJ Suppl,
images, tables and referee report can be found at http://zebu.uoregon.edu/~j
Three-loop HTL gluon thermodynamics at intermediate coupling
We calculate the thermodynamic functions of pure-glue QCD to three-loop order
using the hard-thermal-loop perturbation theory (HTLpt) reorganization of
finite temperature quantum field theory. We show that at three-loop order
hard-thermal-loop perturbation theory is compatible with lattice results for
the pressure, energy density, and entropy down to temperatures .
Our results suggest that HTLpt provides a systematic framework that can used to
calculate static and dynamic quantities for temperatures relevant at LHC.Comment: 24 pages, 13 figs. 2nd version: improved discussion and fixing typos.
Published in JHE
Dynamical spin-flip susceptibility for a strongly interacting ultracold Fermi gas
The Stoner model predicts that a two-component Fermi gas at increasing
repulsive interactions undergoes a ferromagnetic transition. Using the
random-phase approximation we study the dynamical properties of the interacting
Fermi gas. For an atomic Fermi gas under harmonic confinement we show that the
transverse (spin-flip) dynamical susceptibility displays a clear signature of
the ferromagnetic phase in a magnon peak emerging from the Stoner particle-hole
continuum. The dynamical spin susceptibilities could be experimentally explored
via spin-dependent Bragg spectroscopy.Comment: 4 pages, 3 figure
Projectile Excitations in Reactions
It has recently been proven from measurements of the spin-transfer
coefficients and that there is a small but non-vanishing
component , in the inclusive reaction
cross section . It is shown that the dominant part of the measured
can be explained in terms of the projectile excitation
mechanism. An estimate is further made of contributions to from
s-wave rescattering process. It is found that s-wave rescattering contribution
is much smaller than the contribution coming from projectile
excitation mechanism. The addition of s-wave rescattering contribution to the
dominant part, however, improves the fit to the data.Comment: 9 pages, Revtex, figures can be obtained upon reques
Low velocity quantum reflection of Bose-Einstein condensates
We studied quantum reflection of Bose-Einstein condensates at normal
incidence on a square array of silicon pillars. For incident velocities of
2.5-26 mm/s observations agreed with theoretical predictions that the
Casimir-Polder potential of a reduced density surface would reflect slow atoms
with much higher probability. At low velocities (0.5-2.5 mm/s), we observed
that the reflection probability saturated around 60% rather than increasing
towards unity. We present a simple model which explains this reduced
reflectivity as resulting from the combined effects of the Casimir-Polder plus
mean field potential and predicts the observed saturation. Furthermore, at low
incident velocities, the reflected condensates show collective excitations.Comment: 4 figure
Phase Sensitive Recombination of Two Bose-Einstein Condensates on an Atom Chip
The recombination of two split Bose-Einstein condensates on an atom chip is
shown to result in heating which depends on the relative phase of the two
condensates. This heating reduces the number of condensate atoms between 10 and
40% and provides a robust way to read out the phase of an atom interferometer
without the need for ballistic expansion. The heating may be caused by the
dissipation of dark solitons created during the merging of the condensates.Comment: 5 pages, 4 figure
On the Point-Splitting Method of the Commutator Anomaly of the Gauss Law Operators
We analyze the generalized point-splitting method and Jo's result for the
commutator anomaly. We find that certain classes of general regularization
kernels satisfying integral conditions provide a unique result, which, however
differs from Faddeev's cohomological result.Comment: 16 pages, RevTex, 1 figure + 1 table, uses psbox.te
Note on Moufang-Noether currents
The derivative Noether currents generated by continuous Moufang
tranformations are constructed and their equal-time commutators are found. The
corresponding charge algebra turns out to be a birepresentation of the tangent
Mal'ltsev algebra of an analytic Moufang loop.Comment: LaTeX2e, 6 pages, no figures, presented on "The XVth International
Colloquium on Integrable Systems and Quantum Symmetries, Prague, 15-17 June,
2006
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