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تسجيل مستخدم جديدProceedings of the 2nd Iberian Nuclear Astrophysics Meeting on Compact Stars
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This volume contains most of the links to the presentations delivered at this international workshop. This meeting was the second in the series following the previous I Encuentro Iberico de Compstar, held at the University of Coimbra, Portugal in 2010. The main purpose of this meeting was to strengthen the scientific collaboration between the participants of the Iberian and the rest of the southern European branches of the European Nuclear Astrophysics network, formerly, COMPSTAR. This ESF (European Science Foundation) supported network has been crucial in helping to make a broader audience for the the most interesting and relevant research lines being developed currently in Nuclear Astrophysics, especially related to the physics of neutron stars. The program of the meeting was tailored to theoretical descriptions of the physics of neutron stars although some input from experimental observers and other condensed matter and optics areas of interest was also included.
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The equation of state (EoS) of hot and dense matter is a fundamental input to describe static and dynamical properties of neutron stars, core-collapse supernovae and binary compact-star mergers. We review the current status of the EoS for compact obj
ects, that have been studied with both ab-initio many-body approaches and phenomenological models. We limit ourselves to the description of EoSs with purely nucleonic degrees of freedom, disregarding the appearance of strange baryonic matter and/or quark matter. We compare the theoretical predictions with different data coming from both nuclear physics experiments and astrophysical observations. Combining the complementary information thus obtained greatly enriches our insights into the dense nuclear matter properties. Current challenges in the description of the EoS are also discussed, mainly focusing on the model dependence of the constraints extracted from either experimental or observational data (specifically, concerning the symmetry energy), the lack of a consistent and rigorous many-body treatment at zero and finite temperature of the matter encountered in compact stars (e.g. problem of cluster formation and extension of the EoS to very high temperatures), the role of nucleonic three-body forces, and the dependence of the direct URCA processes on the EoS.
We study hybrid stars considering the effects on stellar stability of the hadron-quark conversion speed at the sharp interface. The equation of state is constructed by combining a model-agnostic hadronic description with a constant speed of sound mod
el for quark matter. We show that current LIGO/Virgo, NICER, low-density nuclear and high-density perturbative QCD constraints can be satisfied in two scenarios with low and high transition pressures. If the conversion speed is slow, a new class of hybrid objects is possible and very stiff hadronic equations of state cannot be discarded.
Background: The nuclear symmetry energy $E_{sym}(rho)$ encodes information about the energy necessary to make nuclear systems more neutron-rich. While its slope parameter L at the saturation density $rho_0$ of nuclear matter has been relatively well
constrained by recent astrophysical observations and terrestrial nuclear experiments, its curvature $K_{rm{sym}}$ characterizing the $E_{sym}(rho)$ around $2rho_0$ remains largely unconstrained. Over 520 calculations for $E_{sym}(rho)$ using various nuclear theories and interactions in the literature have predicted several significantly different $K_{rm{sym}}-L$ correlations. Purpose: If a unique $K_{rm{sym}}-L$ correlation of $E_{sym}(rho)$ can be firmly established, it will enable us to progressively better constrain the high-density behavior of $E_{sym}(rho)$ using the available constraints on its slope parameter L. We investigate if and by how much the different $K_{rm{sym}}-L$ correlations may affect neutron star observables. Method: A meta-model of nuclear Equation of States (EOSs) with three representative $K_{rm{sym}}-L$ correlation functions is used to generate multiple EOSs for neutron stars. We then examine effects of the $K_{rm{sym}}-L$ correlation on the crust-core transition density and pressure as well as the radius and tidal deformation of canonical neutron stars. Results:The $K_{rm{sym}}-L$ correlation affects significantly both the crust-core transition density and pressure. It also has strong imprints on the radius and tidal deformability of canonical neutron stars especially at small L values. The available data from LIGO/VIRGO and NICER set some useful limits for the slope L but can not distinguish the three representative $K_{rm{sym}}-L$ correlations considered.
The detection of the GW170817 neutron star merger event has incited an intense research activity towards the understanding of the nuclear matter equation of state. In this paper we compare in particular the pressure-density relation obtained from hea
vy-ion collisions with the analysis of the NS merger event. Moreover, we present recent calculations of neutron stars moment of inertia and tidal deformability using various microscopic equations of state for nuclear and hybrid star configurations, and confirm several universal relations. We also discuss the recent constraints for the NS radii determined by GW170817, and find compatible radii between 12 and 13 kilometers, thus identifying the suitable equations of state.
This booklet contains a collection of contributions to the meeting of the JEts and Disks at INAF (JEDI) group, which took place at the Capodimonte Observatory during 9-10 April 2015. Scope of the meeting was to bring together the JEDI researchers of
the Italian Istituto Nazionale di Astrofisica (INAF) working in the field of circumstellar disks and jets in young stars, to discuss together the different agents affecting the structure and the evolution of disks, namely accretion, jets and winds. More information on the JEDI group and its activities can be found at texttt{http://www.oa-roma.inaf.it/irgroup/JEDI}.
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