Supporting the search for the CEP location with nonlocal PNJL models constrained by Lattice QCD

We investigate the possible location of the critical endpoint in the QCD phase diagram based on nonlocal covariant PNJL models including a vector interaction channel. The form factors of the covariant interaction are constrained by lattice QCD data for the quark propagator. The comparison of our results for the pressure including the pion contribution and the scaled pressure shift $\Delta P / T^4$ vs $T/T_c$ with lattice QCD results shows a better agreement when Lorentzian formfactors for the nonlocal interactions and the wave function renormalization are considered. The strength of the vector coupling is used as a free parameter which influences results at finite baryochemical potential. It is used to adjust the slope of the pseudocritical temperature of the chiral phase transition at low baryochemical potential and the scaled pressure shift accessible in lattice QCD simulations. Our study, albeit presently performed at the meanfield level, supports the very existence of a critical point and favors its location within a region that is accessible in experiments at the NICA accelerator complex.Comment: 7 pages, 7 Figures. Version accepted by Eur. Phys. J. A as part of the topical collection: Exploring strongly interacting matter at high densities - NICA White Pape

Nonlocal chiral quark models with Polyakov loop at finite temperature and chemical potential

We analyze the chiral restoration and deconfinement transitions in the framework of a non-local chiral quark model which includes terms leading to the quark wave function renormalization, and takes care of the effect of gauge interactions by coupling the quarks with the Polyakov loop. Non-local interactions are described by considering both a set of exponential form factors, and a set of form factors obtained from a fit to the mass and renormalization functions obtained in lattice calculations.Comment: 8 pages, 2 figures; prepared for IV International Workshop on Astronomy and Relativistic Astrophysics (IWARA 2009), Maresias, 4-8 Oct 200

Trabajo social familiar: incorporación de la hermenéutica como posibilidad de co-transformación

El presente artículo procura aproximarse a presupuestos epistemológicos que actualmente ofrece la hermenéutica al trabajo social para la intervención en situaciones familiares. El trabajo social debe de aceptar el desafío de búsqueda de nuevos rumbos en la práctica profesional, apuntando a la construcción de alternativas de acción acordes a las circunstancias sociales prevalecientes. Dado que no existe un modelo hegemónico a seguir, el trabajo social familiar se enfrenta a serios retos en la práctica cotidiana. Por tanto, este ensayo propone la incorporación de elementos teóricos hermenéuticos como posibilidad para la interpretación de las acciones sociales

Quark-hybrid matter in the cores of massive neutron stars

Using a nonlocal extension of the SU(3) Nambu-Jona Lasinio model, which reproduces several of the key features of Quantum Chromodynamics, we show that mixed phases of deconfined quarks and confined hadrons (quark-hybrid matter) may exist in the cores of neutron stars as massive as around 2.1 M_Sun. The radii of these objects are found to be in the canonical range of $\sim 12-13$ km. According to our study, the transition to pure quark matter does not occur in stable neutron stars, but is shifted to neutron stars which are unstable against radial oscillations. The implications of our study for the recently discovered, massive neutron star PSR J1614-2230, whose gravitational mass is $1.97 \pm 0.04 M_Sun$, are that this neutron star may contain an extended region of quark-hybrid matter at it center, but no pure quark matter.Comment: 13 pages, 3 figure

Quark deconfinement in high-mass neutron stars

In this paper, we explore whether or not quark deconfinement may occur in high-mass neutron stars such as J1614-2230 (1.97 \pm 0.04 M_Sun) and J0348+0432 (2.01 \pm 0.04 M_Sun). Our study is based on a non-local extension of the SU(3) Nambu Jona-Lasinio (n3NJL) model with repulsive vector interactions among the quarks. This model goes beyond the frequently used local version of the Nambu Jona-Lasinio (NJL) model by accounting for several key features of QCD which are not part of the local model. Confined hadronic matter is treated in the framework of non-linear relativistic mean field theory. We find that both the local as well as the non-local NJL model predict the existence of extended regions of mixed quark-hadron (quark-hybrid) matter in high-mass neutron stars with masses of 2.1 to 2.4 M_Sun. Pure quark matter in the cores of neutron stars is obtained for certain parametrizations of the hadronic lagrangian and choices of the vector repulsion among quarks. The radii of high-mass neutron stars with quark-hybrid matter and/or pure quark matter cores in their centers are found to lie in the canonical range of 12 to 13 km.Comment: 31 pages, 17 figures, PRC accepted versio

Medium induced Lorentz symmetry breaking effects in nonlocal PNJL models

In this paper we detail the thermodynamics of two flavor nonlocal Polyakov-Nambu-Jona-Lasinio models for different parametrizations of the quark interaction regulators. The structure of the model is upgraded in order to allow for terms in the quark selfenergy which violate Lorentz invariance due to the presence of the medium. We examine the critical properties, the phase diagram as well as the equation of state. Furthermore, some aspects of the Mott effect for pions and sigma mesons are discussed explicitly within a nonlocal Polyakov-Nambu-Jona-Lasinio model. In particular, we continued the meson polarization function in the complex energy plane and under certain approximations, we were able to extract the imaginary part as a function of the meson energy. We were not able to calculate the dynamical meson mass, and therefore resorted to a technical study of the temperature dependence of the meson width by replacing the meson energy with the temperature dependent spatial meson mass. Our results show that while the temperature behavior of the meson widths is qualitatively the same for a wide class of covariant regulators, the special case where the nonlocal interactions are introduced via the instanton liquid model singles out with a drastically different behavior.Comment: version to match the one published in PR

Properties of high-density matter in neutron stars

This short review aims at giving a brief overview of various states of matter that have been suggested to exist in the ultra-dense centers of neutron stars. Particular emphasis is put on the role of quark deconfinement in neutron stars and on the possible existence of compact stars made of absolutely stable strange quark matter (strange stars). Astrophysical phenomena, which distinguish neutron stars from quark stars, are discussed and the question of whether or not quark deconfinement may occur in neutron stars is investigated. Combined with observed astrophysical data, such studies are invaluable to delineate the complex structure of compressed baryonic matter and to put firm constraints on the largely unknown equation of state of such matter.Fil: Weber, Fridolin. San Diego State University; Estados Unidos. University of California; Estados UnidosFil: Contrera, Gustavo Aníbal Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Área Física Teórica; Argentina. San Diego State University; Estados UnidosFil: Orsaria, Milva Gabriela. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Área Física Teórica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. San Diego State University; Estados UnidosFil: Spinella, William. San Diego State University. Computational Sciences Research Center; Estados UnidosFil: Zubairi, Omair. San Diego State University. Computational Sciences Research Center; Estados Unido