scholarly journals Role of Δs in determining the properties of neutron stars in parameterized hydrostatic equilibrium

2019 ◽  
Vol 28 (09) ◽  
pp. 1950122 ◽  
Author(s):  
Debashree Sen
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Dense Matter ◽  
Hydrostatic Equilibrium ◽  
Chiral Model ◽  
Equilibrium Conditions ◽  
Self Gravity ◽  
Cold Dense Matter ◽  
Baryonic Mass

The possible existence of [Formula: see text] resonances is inspected in the cold dense matter of neutron star (NS) core in the presence of hyperons. The diverse effects of variation in [Formula: see text] mass on their formation and the equation of state (EoS) are studied in this work with an effective chiral model and the resultant NS properties are calculated with the help of parameterized Tolman–Oppenheimer–Volkoff (PTOV) equations to bring out the two important features of pressure in the context of massive NSs. The [Formula: see text] puzzle is re-explored and resolved taking into account the concept of modified/parametrized inertial pressure and self-gravity in case of massive pulsars like PSR J1614−2230 and PSR J0348-0432. It is seen that although the presence of exotic matter like the hyperons and [Formula: see text] softens the EoS considerably, their presence in massive NSs can be successfully explained with the theory of parametrized hydrostatic equilibrium conditions. The results of this work also satisfy the constraints on [Formula: see text] and [Formula: see text] from the gravitational wave (GW170817) detection of binary NS merger. The constraint on baryonic mass from PSR J0737-3039 is also satisfied with the solutions of the PTOV equations for all the [Formula: see text] masses considered.

scholarly journals Probing the neutron star interior and the Equation of State of cold dense matter with the SKA

2015 ◽  
Author(s):  
Anna Watts ◽  
Cristobal M. Espinoza ◽  
Renxin Xu ◽  
Nils Andersson ◽  
John Antoniadis ◽  
...  
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Dense Matter ◽  
Cold Dense Matter

scholarly journals Equation of state constraints for the cold dense matter inside neutron stars using the cooling tail method

2016 ◽  
Vol 591 ◽  
pp. A25 ◽  
Author(s):  
J. Nättilä ◽  
A. W. Steiner ◽  
J. J. E. Kajava ◽  
V. F. Suleimanov ◽  
J. Poutanen
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
State Constraints ◽  
Dense Matter ◽  
Cold Dense Matter

scholarly journals Role of strangeness to the neutron star mass and cooling

2018 ◽  
Vol 168 ◽  
pp. 04011
Author(s):  
Chang-Hwan Lee ◽  
Yeunhwan Lim ◽  
Chang Ho Hyun ◽  
Kyujin Kwak
Keyword(s):  
Neutron Star ◽  
Dense Matter ◽  
High Density ◽  
Saturation Density ◽  
Strange Quarks ◽  
Star Mass ◽  
Neutron Star Mass ◽  
Neutron Star Cooling

Neutron star provides unique environments for the investigation of the physics of extreme dense matter beyond normal nuclear saturation density. In such high density environments, hadrons with strange quarks are expected to play very important role in stabilizing the system. Kaons and hyperons are the lowest mass states with strangeness among meson and bayron families, respectively. In this work, we investigate the role of kaons and hyperons to the neutron star mass, and discuss their role in the neutron star cooling.

An Equation of State of Cold Dense Matter

1975 ◽  
Vol 53 (3) ◽  
pp. 891-893 ◽  
Author(s):  
A. Nishimura ◽  
Y. Yamaguchi
Keyword(s):  
Equation Of State ◽  
Dense Matter ◽  
Cold Dense Matter

scholarly journals Thermal properties of hot and dense matter: Influence of rapid rotation on protoneutron stars, hot neutron stars, and neutron star merger remnants

2021 ◽  
Vol 252 ◽  
pp. 05004
Author(s):  
Polychronis Koliogiannis ◽  
Charalampos Moustakidis
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Equations Of State ◽  
Interaction Model ◽  
Dense Matter ◽  
Baryon Density ◽  
Dense Nuclear Matter ◽  
Protoneutron Stars

The knowledge of the equation of state is a key ingredient for many dynamical phenomena that depend sensitively on the hot and dense nuclear matter, such as the formation of protoneutron stars and hot neutron stars. In order to accurately describe them, we construct equations of state at FInite temperature and entropy per baryon for matter with varying proton fractions. This procedure is based on the momentum dependent interaction model and state-of-the-art microscopic data. In addition, we investigate the role of thermal and rotation effects on microscopic and macroscopic properties of neutron stars, including the mass and radius, the frequency, the Kerr parameter, the central baryon density, etc. The latter is also connected to the hot and rapidly rotating remnant after neutron star merger. The interplay between these quantities and data from late observations of neutron stars, both isolated and in matter of merging, could provide useful insight and robust constraints on the equation of state of nuclear matter.

scholarly journals Neutron stars from crust to core within the Quark-meson coupling model

2020 ◽  
Vol 232 ◽  
pp. 03001
Author(s):  
S. Antić ◽  
J. R. Stone ◽  
A. W. Thomas
Keyword(s):  
Neutron Star ◽  
Dense Matter ◽  
Building Blocks ◽  
Coupling Model ◽  
Meson Coupling ◽  
Exciting Time ◽  
Cold Dense Matter ◽  
Finite Nuclei ◽  
Outer Crust

Recent years continue to be an exciting time for the neutron star physics, providing many new observations and insights to these natural ‘laboratories’ of cold dense matter. To describe them, there are many models on the market but still none that would reproduce all observed and experimental data. The quark-meson coupling model stands out with its natural inclusion of hyperons as dense matter building blocks, and fewer parameters necessary to obtain the nuclear matter equation of state. The latest advances of the QMC model and its application to the neutron star physics will be presented, within which we build the neutron star’s outer crust from finite nuclei up to the neutron drip line. The appearance of different elements and their position in the crust of a neutron star is explored and compared to the predictions of various models, giving the same quality of the results for the QMC model as for the models when the nucleon structure is not taken into account.

scholarly journals Neural network reconstruction of the dense matter equation of state derived from the parameters of neutron stars

2020 ◽  
Vol 642 ◽  
pp. A78 ◽  
Author(s):  
F. Morawski ◽  
M. Bejger
Keyword(s):  
Neural Network ◽  
Machine Learning ◽  
Neural Networks ◽  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Equations Of State ◽  
Dense Matter ◽  
Data Set ◽  
Global Parameters

Context. Neutron stars are currently studied with an rising number of electromagnetic and gravitational-wave observations, which will ultimately allow us to constrain the dense matter equation of state and understand the physical processes at work within these compact objects. Neutron star global parameters, such as the mass and radius, can be used to obtain the equation of state by directly inverting the Tolman-Oppenheimer-Volkoff equations. Here, we investigate an alternative approach to this procedure. Aims. The aim of this work is to study the application of the artificial neural networks guided by the autoencoder architecture as a method for precisely reconstructing the neutron star equation of state, using their observable parameters: masses, radii, and tidal deformabilities. In addition, we study how well the neutron star radius can be reconstructed using only the gravitational-wave observations of tidal deformability, that is, using quantities that are not related in any straightforward way. Methods. The application of an artificial neural network in the equation-of-state reconstruction exploits the non-linear potential of this machine learning model. Since each neuron in the network is basically a non-linear function, it is possible to create a complex mapping between the input sets of observations and the output equation-of-state table. Within the supervised training paradigm, we construct a few hidden-layer deep neural networks on a generated data set, consisting of a realistic equation of state for the neutron star crust connected with a piecewise relativistic polytropes dense core, with its parameters representative of state-of-the art realistic equations of state. Results. We demonstrate the performance of our machine-learning implementation with respect to the simulated cases with a varying number of observations and measurement uncertainties. Furthermore, we study the impact of the neutron star mass distributions on the results. Finally, we test the reconstruction of the equation of state trained on parametric polytropic training set using the simulated mass–radius and mass–tidal-deformability sequences based on realistic equations of state. Neural networks trained with a limited data set are capable of generalising the mapping between global parameters and equation-of-state input tables for realistic models.

scholarly journals Hyperons in hot dense matter: what do the constraints tell us for equation of state?

2018 ◽  
Vol 35 ◽  
Author(s):  
M. Fortin ◽  
M. Oertel ◽  
C. Providência
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Symmetry Energy ◽  
Nuclear Physics ◽  
Equations Of State ◽  
Dense Matter ◽  
Baryon Octet ◽  
Thermodynamic Quantities ◽  
Binary Neutron Star ◽  
Hot Matter

AbstractFor core-collapse and neutron star merger simulations, it is important to have adequate equations of state which describe dense and hot matter as realistically as possible. We present two newly constructed equations of state including the entire baryon octet, compatible with the main constraints coming from nuclear physics, both experimental and theoretical. One of the equations of state describes cold β-equilibrated neutron stars with a maximum mass of 2 Msun. Results obtained with the new equations of state are compared with the ones of DD2Y, the only existing equation of state containing the baryon octet and satisfying the above constraints. The main difference between our new equations of state and DD2Y is the harder symmetry energy of the latter. We show that the density dependence of the symmetry energy has a direct influence on the amount of strangeness inside hot and dense matter and, consequently, on thermodynamic quantities. We expect that these differences affect the evolution of a proto-neutron star or binary neutron star mergers. We propose also several parameterisations based on the DD2 and SFHo models calibrated to Lambda hypernuclei that satisfy the different constraints.

THE ROLE OF SELF-COUPLINGS OF SCALAR MESONS IN NEUTRON STAR MATTER

2002 ◽  
Vol 17 (21) ◽  
pp. 1335-1344 ◽  
Author(s):  
S. S. POCHA ◽  
A. R. TAURINES ◽  
C. A. Z. VASCONCELLOS ◽  
M. B. PINTO ◽  
M. DILLIG
Keyword(s):  
Neutron Star ◽  
Nuclear Matter ◽  
Degrees Of Freedom ◽  
Scalar Meson ◽  
Dense Matter ◽  
Meson Field ◽  
Static Properties ◽  
Hartree Approximation ◽  
Scalar Meson Field

The influence of nonlinear cubic and quartic self-couplings of the scalar meson field in nuclear matter is investigated. In summing the leading tadpole corrections for the Dirac-vacuum, we compare two approaches, the modified relativistic Hartree approximation, applied to the Walecka model, and the relativistic Hartree approximation, employed to the nonlinear model, respectively. These two approaches render similar expressions for the equation of state of nuclear matter up to the fifth order in the scalar meson field. We find that, by exploring the parameter dependence of the two models, they yield similar results for the bulk static properties of nuclear matter. However, increasing the baryon density the two models start to deviate significantly, such as in the predictions for the maximal mass of a neutron star or in the role of hyperon degrees of freedom in dense matter. The results indicate that with increasing density, scalar meson self-couplings beyond the fourth order seem to play a significant role.

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