2,963 research outputs found
Thermal Conductivity and Chiral Critical Point in Heavy Ion Collisions
Background: Quantum Chromodynamics is expected to have a phase transition in
the same static universality class as the 3D Ising model and the liquid-gas
phase transition. The properties of the equation of state, the transport
coefficients, and especially the location of the critical point are under
intense theoretical investigation. Some experiments are underway, and many more
are planned, at high energy heavy ion accelerators. Purpose: Develop a model of
the thermal conductivity, which diverges at the critical point, and use it to
study the impact of hydrodynamic fluctuations on observables in high energy
heavy ion collisions. Methods: We apply mode coupling theory, together with a
previously developed model of the free energy that incorporates the critical
exponents and amplitudes, to construct a model of the thermal conductivity in
the vicinity of the critical point. The effect of the thermal conductivity on
correlation functions in heavy ion collisions is studied in a boost invariant
hydrodynamic model via fluctuations, or noise. Results: We find that the closer
a thermodynamic trajectory comes to the critical point the greater is the
magnitude of the fluctuations in thermodynamic variables and in the 2-particle
correlation functions in momentum space. Conclusions: It may be possible to
discern the existence of a critical point, its location, and thermodynamic and
transport properties near to it in heavy ion collisions using the methods
developed here.Comment: 36 pages, 8 figures. Version published in Phys.Rev.C86, 054911
(2012). It contains some minor improvements with respect to v1: further
clarifications, small changes on figures and two extra reference
Hydrogen-like Atoms from Ultrarelativistic Nuclear Collisions
The number of hydrogen-like atoms produced when heavy nuclei collide is
estimated for central collisions at the Relativistic Heavy Ion Collider using
the sudden approximation of Baym et al. As first suggested by Schwartz, a
simultaneous measurement of the hydrogen and hadron spectra will allow an
inference of the electron or muon spectra at low momentum where a direct
experimental measurement is not feasible.Comment: 6 pages, 4 figure
Effect of the Haar measure on the finite temperature effective potential of Yang-Mills theory
Including the Haar measure we show that the effective potential of the
regularized SU(2) Yang-Mills theory has a minimum at vanishing Wilson-line
for strong coupling, whereas it develops two degenerate minima close to
for weak coupling. This suggests that the non-abelian character of
as contained in the Haar measure might be responsible for confinement.Comment: 3 pages, LATEX, 1 figure, figure available upon reques
Effective models of two-flavor QCD: from small towards large
We study effective models of chiral fields and Polyakov loop expected to
describe the dynamics responsible for the phase structure of two-flavor QCD. We
consider chiral sector described either using linear sigma model or
Nambu-Jona-Lasinio model and study how these models, on the mean-field level
when coupled with the Polyakov loop, behave as a function of increasing bare
quark (or pion) mass. We find qualitatively similar behaviors for the cases of
linear sigma model and Nambu-Jona-Lasinio model and, relating to existing
lattice data, show that one cannot conclusively decide which or the two
approximate symmetries drives the phase transitions near the physical point
A PNJL model in 0+1 Dimensions
We formulate the Polyakov-Nambu-Jona-Lasinio (PNJL) model in 0+1 dimensions.
The thermodynamics captured by the partition function yields a bulk pressure,
as well as quark susceptibilities versus temperature that are similar to the
ones in 3+1 dimensions. Around the transition temperature the behavior in the
pressure and quark susceptibilities follows from the interplay between the
lowest Matsubara frequency and the Polyakov line. The reduction to the lowest
Matsubara frequency yields a matrix Model. In the presence of the Polyakov line
the UV part of the Dirac spectrum features oscillations when close to the
transition temperature.Comment: 18 pages, 13 figure
On the imaginary parts and infrared divergences of two-loop vector boson self-energies in thermal QCD
We calculate the imaginary part of the retarded two-loop self-energy of a
static vector boson in a plasma of quarks and gluons of temperature T, using
the imaginary time formalism. We recombine various cuts of the self-energy to
generate physical processes. We demonstrate how cuts containing loops may be
reinterpreted in terms of interference between Order tree diagrams and
the Born term along with spectators from the medium. We apply our results to
the rate of dilepton production in the limit of dilepton invariant mass E>>T.
We find that all infrared and collinear singularities cancel in the final
result obtained in this limit.Comment: references added, typos corrected, slightly abridged, version
accepted for publication in Phys. Rev.
Nucleus-Nucleus Bremsstrahlung from Ultrarelativistic Collisions
The bremsstrahlung produced when heavy nuclei collide is estimated for
central collisions at the Relativistic Heavy Ion Collider. Soft photons can be
used to infer the rapidity distribution of the outgoing charge. An experimental
design is outlined.Comment: 12 pages, 7 figures, uses revte
SU(2) Chiral Sigma Model Study of Phase Transition in Hybrid Stars
We use a modified SU(2) chiral sigma model to study nuclear matter component
and simple bag model for quark matter constituting a neutron star. We also
study the phase transition of nuclear matter to quark matter with the mixed
phase characterized by two conserved charges in the interior of highly dense
neutron stars. Stable solutions of Tolman-Oppenheimer-Volkoff equations
representing hybrid stars are obtained with a maximum mass of 1.67
and radius around 8.9 km.Comment: 14 pages, 5 figure
Bose-Einstein Condensation in the Relativistic Ideal Bose Gas
The Bose-Einstein condensation (BEC) critical temperature in a relativistic
ideal Bose gas of identical bosons, with and without the antibosons expected to
be pair-produced abundantly at sufficiently hot temperatures, is exactly
calculated for all boson number-densities, all boson point rest masses, and all
temperatures. The Helmholtz free energy at the critical BEC temperature is
found to be lower, thus implying that the omission of antibosons always leads
to the computation of a metastable state.Comment: 10 pages, 4 figure
Symmetric and anti-symmetric Landau parameters and magnetic properties of dense quark matter
We calculate the dimensionless Fermi liquid parameters (FLPs),
and , for spin asymmetric dense quark matter.
In general, the FLPs are infrared divergent due to the exchange of massless
gluons. To remove such divergences, the Hard Density Loop (HDL) corrected gluon
propagator is used. The FLPs so determined are then invoked to calculate
magnetic properties such as magnetization and magnetic
susceptibility of spin polarized quark matter. Finally, we investigate
the possibility of magnetic instability by studying the density dependence of
and .Comment: 14 pages, 5 figures, abstract and introduction modifified. Published
in Phys. Rev. C. 81, 054906 (2010
- …