366 research outputs found
Stability windows for proto-quark stars
We investigate the existence of possible stable strange matter and related
stability windows at finite temperature for different models that are generally
applied to describe quark stars, namely, the quark-mass density dependent
model, the MIT bag model and the Nambu-Jona-Lasinio model. We emphasize that,
although the limits for stable strange matter depend on a comparison with the
ground state of 56Fe, which is a zero temperature state, the quantity that has
to be used in the search for strange matter in proto-quark stars is the free
energy and we analyze stability windows up to temperatures of the order of 40
MeV. The effects of strong magnetic fields on stability windows are computed
and the resulting mass-radius relations for different stages of the proto-quark
star are analyzed.Comment: Published versio
Proto-Neutron and Neutron Stars in a Chiral SU(3) Model
A hadronic chiral SU(3) model is applied to neutron and proto-neutron stars,
taking into account trapped neutrinos, finite temperature and entropy. The
transition to the chirally restored phase is studied and global properties of
the stars like minimum and maximum masses and radii are calculated for
different cases. In addition, the effects of rotation on neutron star masses
are included and the conservation of baryon number and angular momentum
determine the maximum frequencies of rotation during the cooling
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
Delta Baryons in Neutron-Star Matter under Strong Magnetic Fields
In this work, we study magnetic field effects on neutron star matter
containing the baryon octet and additional heavier spin 3/2 baryons (the
's). We make use of two different relativistic hadronic models that
contain an additional vector-isovector self interaction for the mesons: one
version of a relativistic mean field (RMF) model and the Chiral Mean Field
(CMF) model. We find that both the additional interaction and a strong magnetic
field enhance the baryon population in dense matter, while decreasing
the relative density of hyperons. At the same time that the vector-isovector
meson interaction modifies neutron-star masses very little (), it
decreases their radii considerably, allowing both models to be in better
agreement with observations. Together, these features indicate that magnetic
neutron stars are likely to contain baryons in their interior.Comment: 9 pages, 8 figure
Hybrid Stars in an SU(3) Parity Doublet Model
We apply an extended version of the SU(3) parity model, containing quark
degrees of freedom, to study neutron stars. The model successfully reproduces
the main thermodynamic features of QCD which allows us to describe the
composition of dense matter. Chiral symmetry restoration is realized inside the
star and the chiral partners of the baryons appear, their masses becoming
degenerate. Furthermore, quark degrees of freedom appear in a transition to a
deconfined state. Performing an investigation of the macroscopic properties of
neutron stars, we show that observational constraints, like mass and thermal
evolution, are satisfied and new predictions can be made
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
- …