240 research outputs found
Properties and Stability of Hybrid Stars
We discuss the properties of neutron stars and their modifications due to the
occurrence of hyperons and quarks in the core of the star. More specifically,
we consider the general problem of exotic particles inside compact stars in
light of the observed two-solar mass pulsar. In addition, we investigate
neutron star cooling and a possible explanation of the recently measured
cooling curve of the neutron star in the supernova remnant Cas A.Comment: Contribution to SQM 2011 in Krak\'o
Chiral thermodynamics of dense hadronic matter
We discuss phases of hot and dense hadronic matter using chiral Lagrangians.
A two-flavored parity doublet model constrained by the nuclear matter ground
state predicts chiral symmetry restoration. The model thermodynamics is shown
within the mean field approximation. A field-theoretical constraint on possible
phases from the anomaly matching is also discussed.Comment: 8 pages, 2 figures, to appear in the proceedings of 6th International
Workshop on Critical Point and Onset of Deconfinement (CPOD), 23-29 August
2010 at Joint Institute for Nuclear Research, Dubna, Russi
Compact Stars - How Exotic Can They Be?
Strong interaction physics under extreme conditions of high temperature
and/or density is of central interest in modern nuclear physics for
experimentalists and theorists alike. In order to investigate such systems,
model approaches that include hadrons and quarks in a unified approach, will be
discussed. Special attention will be given to high-density matter as it occurs
in neutron stars. Given the current observational limits for neutron star
masses, the properties of hyperonic and hybrid stars will be determined. In
this context especially the question of the extent, to which exotic particles
like hyperons and quarks affect star masses, will be discussed.Comment: Contributon to conference "Nuclear Physics: Present and Future", held
in Boppard (Germany), May 201
Hybrid Stars in a Strong Magnetic Field
We study the effects of high magnetic fields on the particle population and
equation of state of hybrid stars using an extended hadronic and quark SU(3)
non-linear realization of the sigma model. In this model the degrees of freedom
change naturally from hadrons to quarks as the density and/or temperature
increases. The effects of high magnetic fields and anomalous magnetic moment
are visible in the macroscopic properties of the star, such as mass, adiabatic
index, moment of inertia, and cooling curves. Moreover, at the same time that
the magnetic fields become high enough to modify those properties, they make
the star anisotropic.Comment: Revised version with updated reference
Effective Model Approach to the Dense State of QCD Matter
The first-principle approach to the dense state of QCD matter, i.e. the
lattice-QCD simulation at finite baryon density, is not under theoretical
control for the moment. The effective model study based on QCD symmetries is a
practical alternative. However the model parameters that are fixed by hadronic
properties in the vacuum may have unknown dependence on the baryon chemical
potential. We propose a new prescription to constrain the effective model
parameters by the matching condition with the thermal Statistical Model. In the
transitional region where thermal quantities blow up in the Statistical Model,
deconfined quarks and gluons should smoothly take over the relevant degrees of
freedom from hadrons and resonances. We use the Polyakov-loop coupled
Nambu--Jona-Lasinio (PNJL) model as an effective description in the quark side
and show how the matching condition is satisfied by a simple ansatz on the
Polyakov loop potential. Our results favor a phase diagram with the chiral
phase transition located at slightly higher temperature than deconfinement
which stays close to the chemical freeze-out points.Comment: 8 pages, 4 figures; Talk at International Workshop on High Density
Nuclear Matter, Cape Town, South Africa, April 6-9, 201
Phase diagrams in nonlocal PNJL models constrained by Lattice QCD results
Based on lattice QCD-adjusted SU(2) nonlocal Polyakov--Nambu--Jona-Lasinio
(PNJL) models, we investigate how the location of the critical endpoint in the
QCD phase diagram depends on the strenght of the vector meson coupling, as well
as the Polyakov-loop (PL) potential and the form factors of the covariant
model. The latter are constrained by lattice QCD data for the quark propagator.
The strength of the vector coupling is adjusted such as to reproduce the slope
of the pseudocritical temperature for the chiral phase transition at low
chemical potential extracted recently from lattice QCD simulations. Our study
supports the existence of a critical endpoint in the QCD phase diagram albeit
the constraint for the vector coupling shifts its location to lower
temperatures and higher baryochemical potentials than in the case without it.Comment: 23 pages, 10 figures. Version accepted in Phys. Part. Nucl. Lett. (to
appear), references adde
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