26,800 research outputs found
Three-loop HTLpt thermodynamics at finite temperature and chemical potential
In this proceedings we present a state-of-the-art method of calculating
thermodynamic potential at finite temperature and finite chemical potential,
using Hard Thermal Loop perturbation theory (HTLpt) up to
next-to-next-leading-order (NNLO). The resulting thermodynamic potential
enables us to evaluate different thermodynamic quantities including pressure
and various quark number susceptibilities (QNS). Comparison between our
analytic results for those thermodynamic quantities with the available lattice
data shows a good agreement.Comment: 5 pages, 6 figures, conference proceedings of XXI DAE-BRNS HEP
Symposium, IIT Guwahati, December 2014; to appear in 'Springer Proceedings in
Physics Series
An interpolatory ansatz captures the physics of one-dimensional confined Fermi systems
Interacting one-dimensional quantum systems play a pivotal role in physics.
Exact solutions can be obtained for the homogeneous case using the Bethe ansatz
and bosonisation techniques. However, these approaches are not applicable when
external confinement is present. Recent theoretical advances beyond the Bethe
ansatz and bosonisation allow us to predict the behaviour of one-dimensional
confined systems with strong short-range interactions, and new experiments with
cold atomic Fermi gases have already confirmed these theories. Here we
demonstrate that a simple linear combination of the strongly interacting
solution with the well-known solution in the limit of vanishing interactions
provides a simple and accurate description of the system for all values of the
interaction strength. This indicates that one can indeed capture the physics of
confined one-dimensional systems by knowledge of the limits using wave
functions that are much easier to handle than the output of typical numerical
approaches. We demonstrate our scheme for experimentally relevant systems with
up to six particles. Moreover, we show that our method works also in the case
of mixed systems of particles with different masses. This is an important
feature because these systems are known to be non-integrable and thus not
solvable by the Bethe ansatz technique.Comment: 22 pages including methods and supplementary materials, 11 figures,
title slightly change
Solar-Like Cycle in Asymptotic Giant Branch Stars
I propose that the mechanism behind the formation of concentric semi-periodic
shells found in several planetary nebulae (PNs) and proto-PNs, and around one
asymptotic giant branch (AGB) star, is a solar-like magnetic activity cycle in
the progenitor AGB stars. The time intervals between consecutive ejection
events is about 200-1,000 years, which is assumed to be the cycle period (the
full magnetic cycle can be twice as long, as is the 22-year period in the sun).
The magnetic field has no dynamical effects; it regulates the mass loss rate by
the formation of magnetic cool spots. The enhanced magnetic activity at the
cycle maximum results in more magnetic cool spots, which facilitate the
formation of dust, hence increasing the mass loss rate. The strong magnetic
activity implies that the AGB star is spun up by a companion, via a tidal or
common envelope interaction. The strong interaction with a stellar companion
explains the observations that the concentric semi-periodic shells are found
mainly in bipolar PNs.Comment: 10 pages, submitted to Ap
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
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
The mass content of the Sculptor dwarf spheroidal galaxy
We present a new determination of the mass content of the Sculptor dwarf
spheroidal galaxy, based on a novel approach which takes into account the two
distinct stellar populations present in this galaxy. This method helps to
partially break the well-known mass-anisotropy degeneracy present in the
modelling of pressure-supported stellar systems.Comment: 6 pages, 3 figures. To appear in the proceedings of IAU Symposium 254
"The Galaxy disk in a cosmological context", Copenhagen, June 200
Verifying continuous variable entanglement of intense light pulses
Three different methods have been discussed to verify continuous variable
entanglement of intense light beams. We demonstrate all three methods using the
same set--up to facilitate the comparison. The non--linearity used to generate
entanglement is the Kerr--effect in optical fibres. Due to the brightness of
the entangled pulses, standard homodyne detection is not an appropriate tool
for the verification. However, we show that by using large asymmetric
interferometers on each beam individually, two non-commuting variables can be
accessed and the presence of entanglement verified via joint measurements on
the two beams. Alternatively, we witness entanglement by combining the two
beams on a beam splitter that yields certain linear combinations of quadrature
amplitudes which suffice to prove the presence of entanglement.Comment: 11 pages, 7 figures, to appear in Phys. Rev.
Antiferromagnetic noise correlations in optical lattices
We analyze how noise correlations probed by time-of-flight (TOF) experiments
reveal antiferromagnetic (AF) correlations of fermionic atoms in
two-dimensional (2D) and three-dimensional (3D) optical lattices. Combining
analytical and quantum Monte Carlo (QMC) calculations using experimentally
realistic parameters, we show that AF correlations can be detected for
temperatures above and below the critical temperature for AF ordering. It is
demonstrated that spin-resolved noise correlations yield important information
about the spin ordering. Finally, we show how to extract the spin correlation
length and the related critical exponent of the AF transition from the noise.Comment: 4 pages, 4 figure
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