778 research outputs found
Deconfinement of neutron star matter within the Nambu-Jona-Lasinio model
We study the deconfinement transition of hadronic matter into quark matter
under neutron star conditions assuming color and flavor conservation during the
transition. We use a two-phase description. For the hadronic phase we use
different parameterizations of a non-linear Walecka model which includes the
whole baryon octet. For the quark matter phase we use an SU(3)_f
Nambu-Jona-Lasinio effective model including color superconductivity.
Deconfinement is considered to be a first order phase transition that conserves
color and flavor. It gives a short-lived transitory colorless-quark-phase that
is not in beta-equilibrium, and decays to a stable configuration in tau ~
tau_{weak} ~ 10^{-8} s. However, in spite of being very short lived, the
transition to this intermediate phase determines the onset of the transition
inside neutron stars. We find the transition free-energy density for
temperatures typical of neutron star interiors. We also find the critical mass
above which compact stars should contain a quark core and below which they are
safe with respect to a sudden transition to quark matter. Rather independently
on the stiffness of the hadronic equation of state (EOS) we find that the
critical mass of hadronic stars (without trapped neutrinos) is in the range of
~ 1.5 - 1.8 solar masses. This is in coincidence with previous results obtained
within the MIT Bag model.Comment: 10 pages, 2 figure
Phase diagram of neutron star quark matter in nonlocal chiral models
We analyze the phase diagram of two-flavor quark matter under neutron star
constraints for a nonlocal covariant quark model within the mean field
approximation. Applications to cold compact stars are discussed.Comment: 3 pages, 1 figure, proceedings of the IV International Conference on
Quarks and Nuclear Physics (QNP06), Madrid, Spain, June 5-10, 2006. To appear
in Eur. Phys. J.
Color neutrality effects in the phase diagram of the PNJL model
The phase diagram of a two-flavor Polyakov loop Nambu-Jona-Lasinio model is
analyzed imposing the constraint of color charge neutrality. Main effects of
this constraint are a shrinking of the chiral symmetry breaking (chiSB) domain
in the T-mu plane, a shift of the critical point to lower temperatures and a
coexistence of chiSB and two-flavor superconducting phases. The effects can be
understood in view of the presence of a nonvanishing color chemical potential
mu_8, which is necessary to compensate the color charge density rho_8 induced
by the nonvanishing Polyakov-loop mean field phi_3.Comment: 8 pages, 4 figures, figures added, minor text modification
Deconfinement transition in protoneutron stars: analysis within the Nambu-Jona-Lasinio model
We study the effect of color superconductivity and neutrino trapping on the
deconfinement transition of hadronic matter into quark matter in a protoneutron
star. To describe the strongly interacting matter a two-phase picture is
adopted. For the hadronic phase we use different parameterizations of a
non-linear Walecka model which includes the whole baryon octet. For the quark
matter phase we use an Nambu-Jona-Lasinio effective model which
includes color superconductivity. We impose color and flavor conservation
during the transition in such a way that just deconfined quark matter is
transitorily out of equilibrium with respect to weak interactions. We find that
deconfinement is more difficult for small neutrino content and it is easier for
lower temperatures although these effects are not too large. In addition they
will tend to cancel each other as the protoneutron star cools and deleptonizes,
resulting a transition density that is roughly constant along the evolution of
the protoneutron star. According to these results the deconfinement transition
is favored after substantial cooling and contraction of the protoneutron star
Third family of compact stars within a nonlocal chiral quark model equation of state
A class of hybrid compact star equations of state is investigated that joins by a Maxwell construction a low-density phase of hadronic matter, modeled by a relativistic mean-field approach with excluded nucleon volume, with a high-density phase of color superconducting two-flavor quark matter, described within a nonlocal covariant chiral quark model. It is found that the occurrence of a stable branch of hybrid compact stars requires a nonvanishing vector meson coupling in the quark model that exceeds a minimal value which depends on the presence of a diquark condensate. It is shown that these hybrid stars do not form a third family disconnected from the second family of ordinary neutron stars unless additional (de)confining effects are introduced with a density-dependent bag pressure. A suitably chosen density dependence of the vector meson coupling assures that at the same time the 2 M maximum mass constraint is fulfilled on the hybrid star branch. A twofold interpolation method is realized which implements both the density dependence of a confining bag pressure at the onset of the hadron-to-quark matter transition and the stiffening of quark matter at higher densities by a density-dependent vector meson coupling. For three parametrizations of this class of hybrid equation of state the properties of corresponding compact star sequences are presented, including mass twins of neutron and hybrid stars at 2.00, 1.39 and 1.20 M, respectively, and the hybrid compact star (third) families. The sensitivity of the hybrid equation of state and the corresponding compact star sequences to variations of the interpolation parameters at the 10% level is investigated and it is found that the feature of third family solutions for compact stars is robust against such a variation. This advanced description of hybrid star matter allows us to interpret GW170817 as a merger not only of two neutron stars but also of a neutron star with a hybrid star or of two hybrid stars.Fil: Alvarez Castillo, D. E.. Bogoliubov Laboratory Of Theoretical Physics; Rusia. Universidad AutĂłnoma de San Luis PotosĂ; MĂ©xicoFil: Blaschke, D. B.. Bogoliubov Laboratory For Theoretical Physics; Rusia. University Of Wroclaw; PoloniaFil: Grunfeld, Ana Gabriela. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. ComisiĂłn Nacional de EnergĂa AtĂłmica; ArgentinaFil: Pagura, V. P.. Universidad de Valencia; Españ
Hybrid stars within a covariant, nonlocal chiral quark model
We present a hybrid equation of state (EoS) for dense matter in which a nuclear matter phase is described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach and a two-flavor quark matter phase is modelled according to a recently developed covariant, nonlocal chiral quark model. We show that modern observational constraints for compact star masses (M ~ 2 M_sun) can be satisfied when a small vector-like four quark interaction is taken into account. The corresponding isospin symmetric EoS is consistent with flow data analyses of heavy ion collisions and points to a deconfinement transition at about 0.55 fm^-3
Wage losses in the year after breast cancer: Extent and determinants among Canadian women
This article is available open access through the publisher’s website at the link below. © The Author 2008.Background - Wage losses after breast cancer may result in considerable financial burden. Their assessment is made more urgent because more women now participate in the workforce and because breast cancer is managed using multiple treatment modalities that could lead to long work absences. We evaluated wage losses, their determinants, and the associations between wage losses and changes for the worse in the family's financial situation among Canadian women over the first 12 months after diagnosis of early breast cancer.
Methods - We conducted a prospective cohort study among women with breast cancer from eight hospitals throughout the province of Quebec. Information that permitted the calculation of wage losses and information on potential determinants of wage losses were collected by three pretested telephone interviews conducted over the year following the start of treatment. Information on medical characteristics was obtained from medical records. The main outcome was the proportion of annual wages lost because of breast cancer. Multivariable analysis of variance using the general linear model was used to identify personal, medical, and employment characteristics associated with the proportion of wages lost. All statistical tests were two-sided.
Results - Among 962 eligible breast cancer patients, 800 completed all three interviews. Of these, 459 had a paying job during the month before diagnosis. On average, these working women lost 27% of their projected usual annual wages (median = 19%) after compensation received had been taken into account. Multivariable analysis showed that a higher percentage of lost wages was statistically significantly associated with a lower level of education (Ptrend = .0018), living 50 km or more from the hospital where surgery was performed (P = .070), lower social support (P = .012), having invasive disease (P = .086), receipt of chemotherapy (P < .001), self-employment (P < .001), shorter tenure in the job (Ptrend < .001), and part-time work (P < .001).
Conclusion - Wage losses and their effects on financial situation constitute an important adverse consequence of breast cancer in Canada.The Canadian Breast Cancer Research Alliance, Canadian
Institutes of Health Research, and Fondation de l’Université Laval
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