220 research outputs found
Compact Stars in Hadron and Quark-Hadron Models
We investigate strongly interacting dense matter and neutron stars using a
flavor-SU(3) approach based on a non-linear realization of chiral symmetry as
well as a hadronic flavor-SU(2) parity-doublet model. We study chiral symmetry
restoration and the equation of state of stellar matter and determine neutron
star properties using different sets of degrees of freedom. Finally, we include
quarks in the model approach. We show the resulting phase diagram as well as
hybrid star solutions for this model.Comment: conference proceedings Iwara 200
The application of the Quark-Hadron Chiral Parity-Doublet Model to neutron star matter
The Quark-Hadron Chiral Parity-Doublet model (QP) is applied to
calculate compact star properties in the presence of a deconfinement phase
transition. Within this model, a consistent description of nuclear matter
properties, chiral symmetry restoration, and a transition from hadronic to
quark and gluonic degrees of freedom is possible within one unified approach.
We find that the equation of state obtained is consistent with recent
perturbative quantum chromodynamics (QCD) results and is able to accommodate
observational constraints of massive and small neutron stars. Furthermore, we
show that important features of the equation of state, such as the symmetry
energy and its slope, are well within their observational constraints.Comment: 8 pages, 9 figures and 1 tabl
Modeling Hybrid Stars with an SU(3) non-linear sigma model
We study the behavior of hybrid stars using an extended hadronic and quark
SU(3) non-linear sigma model. The degrees of freedom change naturally, in this
model, from hadrons to quarks as the density/temperature increases. At zero
temperature, we reproduce massive neutron stars containing a core of hybrid
matter of 2 km for the non-rotating case and 1.18 km and 0.87 km, in the
equatorial and polar directions respectively, for stars rotating at the Kepler
frequency (physical cases lie in between). The cooling of such stars is also
analyzed.Comment: Revised version, references and figures added. Accepted for
publication in Physical Review
Quark core impact on hybrid star cooling
In this paper we investigate the thermal evolution of hybrid stars, objects
composed of a quark matter core, enveloped by ordinary hadronic matter. Our
purpose is to investigate how important are the microscopic properties of the
quark core to the thermal evolution of the star. In order to do that we use a
simple MIT bag model for the quark core, and a relativistic mean field model
for the hadronic envelope. By choosing different values for the microscopic
parameters (bag constant, strange quark mass, strong coupling constant) we
obtain hybrid stars with different quark core properties. We also consider the
possibility of color superconductivity in the quark core. With this simple
approach, we have found a set of microscopic parameters that lead to a good
agreement with observed cooling neutron stars. Our results can be used to
obtain clues regarding the properties of the quark core in hybrid stars, and
can be used to refine more sophisticated models for the equation of state of
quark matter.Comment: 8 pages, 10 figures. Accepted for publication in Physical Review
A Novel Approach to Model Hybrid Stars
We extend the hadronic SU(3) non-linear sigma model to include quark degrees
of freedom. The choice of potential for the Polyakov loop as a function of
temperature and chemical potential allows us to construct a realistic phase
diagram from the analysis of the order parameters of the system. These
parameters are the chiral condensate, for the chiral symmetry restoration and
the Polyakov loop, for the deconfinement to quark matter. Besides reproducing
lattice QCD results, for zero and low chemical potential, we are in agreement
with neutron star observations for zero temperature
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