1,683 research outputs found
Magnetic aspects of QCD at finite density and temperature
Some magnetic aspects of QCD are discussed at finite density and temperature.
Possibility of spontaneous magnetization is studied within Landau Fermi-liquid
theory, and the important roles of the screening effects for gluon propagation
are elucidated. Static screening for the longitudinal gluons improves the
infrared singularities, while the transverse gluons receive only dynamic
screening. The latter property gives rise to a novel non-Fermi-liquid behaviour
for the magnetic susceptibility. Appearance of a density-wave state is also
discussed in relation to chiral transition, where pseudoscalar condensate as
well as scalar one takes a spatially non-uniform form in a chirally invariant
way. Accordingly magnetization of quark matter oscillates like spin density
wave. A hadron-quark continuity is suggested in this aspect, remembering pion
condensation in hadronic phase.Comment: 6 pages, 8 figures, Proc. of INPN2010 to appear in J. Phy
Propagation of hydrodynamic interactions between particles in a compressible fluid
Hydrodynamic interactions are transmitted by viscous diffusion and sound
propagation: the temporal evolution of hydrodynamic interactions by both
mechanisms is studied by direct numerical simulation in this paper. The
hydrodynamic interactions for a system of two particles in a fluid are
estimated by the velocity correlation of the particles. In an incompressible
fluid, hydrodynamic interactions propagate instantaneously at the infinite
speed of sound, followed by the temporal evolution of viscous diffusion. On the
other hand, in a compressible fluid, sound propagates at a finite speed, which
affects the temporal evolution of the hydrodynamic interactions by the order of
magnitude relation between the time scales of viscous diffusion and sound
propagation. The hydrodynamic interactions are characterized by introducing the
ratio of these time scales as an interactive compressibility factor.Comment: 12 pages, 8 figure
Direct numerical simulation of dispersed particles in a compressible fluid
We present a direct numerical simulation method for investigating the
dynamics of dispersed particles in a compressible solvent fluid. The validity
of the simulation is examined by calculating the velocity relaxation of an
impulsively forced spherical particle with a known analytical solution. The
simulation also gives information about the fluid motion, which provides some
insight into the particle motion. Fluctuations are also introduced by random
stress, and the validity of this case is examined by comparing the calculation
results with the fluctuation-dissipation theorem.Comment: 7 pages, 5 figure
Finite-size effects at the hadron-quark transition and heavy hybrid stars
We study the role of finite-size effects at the hadron-quark phase transition
in a new hybrid equation of state constructed from an ab-initio
Br\"uckner-Hartree-Fock equation of state with the realistic Bonn-B potential
for the hadronic phase and a covariant non-local Nambu--Jona-Lasinio model for
the quark phase. We construct static hybrid star sequences and find that our
model can support stable hybrid stars with an onset of quark matter below and a maximum mass above in agreement with recent
observations. If the finite-size effects are taken into account the core is
composed of pure quark matter. Provided that the quark vector channel
interaction is small, and the finite size effects are taken into account, quark
matter appears at densities 2-3 times the nuclear saturation density. In that
case the proton fraction in the hadronic phase remains below the value required
by the onset of the direct URCA process, so that the early onset of quark
matter shall affect on the rapid cooling of the star.Comment: version to match the one published in PR
Finite size effects on kaonic pasta structures
Non-uniform structures of mixed phases at the first-order phase transition to
charged kaon condensation are studied using a density functional theory within
the relativistic mean field model. Including electric field effects and
applying the Gibbs conditions in a proper way, we numerically determine density
profiles of nucleons, electrons and condensed kaons. Importance of charge
screening effects is elucidated and thereby we show that the Maxwell
construction is effectively justified. Surface effect is also studied to figure
out its effect on the density profiles
Neutrino Opacities in Neutron Stars with Kaon Condensates
The neutrino mean free paths in hot neutron-star matter are obtained in the
presence of kaon condensates. The kaon-induced neutrino absorption process,
which is allowed only in the presence of kaon condensates, is considered for
both nondegenerate and degenerate neutrinos. The neutrino mean free path due to
this process is compared with that for the neutrino-nucleon scattering. While
the mean free path for the kaon-induced neutrino absorption process is shown to
be shorter than the ordinary two-nucleon absorption process by several orders
of magnitude when temperature is not very high, the neutrino-nucleon scattering
process has still a dominant contribution to the neutrino opacity. Thus, the
kaon-induced neutrino absorption process has a minor effect on the thermal and
dynamical evolution of protoneutron stars.Comment: 35 pages, 4 figure
Hadron-quark mixed phase in hyperon stars
We analyze the different possibilities for the hadron-quark phase transition
occurring in beta-stable matter including hyperons in neutron stars. We use a
Brueckner-Hartree-Fock approach including hyperons for the hadronic equation of
state and a generalized MIT bag model for the quark part. We then point out in
detail the differences between Maxwell and Gibbs phase transition constructions
including the effects of surface tension and electromagnetic screening. We find
only a small influence on the maximum neutron star mass, whereas the radius of
the star and in particular its internal structure are more affected.Comment: 11 pages, 9 figure
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