Selected Papers from “The Modern Physics of Compact Stars and Relativistic Gravity 2019”

A special issue of Particles (ISSN 2571-712X).

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 18210

Special Issue Editor

Special Issue Information

Dear colleagues,

I am happy to announce that selected papers from the work presented at the international conference “The Modern Physics of Compact Stars and Relativistic Gravity 2019” (https://indico.cern.ch/event/769736/) will be published in this Special Issue of Particles, an MDPI open-access journal. The papers submitted to this Special Issue are expected to reflect original work or be a balanced review of a field. All submissions will be peer-reviewed by internationally recognized experts.

The conference series “The Modern Physics of Compact Stars and Relativistic Gravity”, which was started in 2008, is centered on the astrophysics of compact objects, the physics of dense matter, gravitation and cosmology, observations of pulsars, and gravitational waves. The last topic is of special interest due to the observation of binary neutron star inspirals by the LIGO-VIRO collaboration in August 2017. Thus, the current edition is special as it is the first one that takes place in the era of multimessenger astronomy.

As the Guest Editor, I would like to invite you to submit your unpublished and original research relevant to this topic for publication in this Special Issue of Particles. The Article Processing Charge (APC) for submissions from the conference will be free of charge.

Prof. Armen Sedrakian
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Particles is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (7 papers)

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8 pages, 272 KiB  
Article
Reduction of the Mass of the Proto-Quark Star during Cooling
by Gevorg Hajyan
Particles 2021, 4(1), 37-44; https://doi.org/10.3390/particles4010004 - 06 Jan 2021
Cited by 3 | Viewed by 1873
Abstract
The integral parameters (mass, radius) of hot proto-quark stars that are formed in supernova explosion are studied. We use the MIT bag model to determine the pressure of up-down and strage quark matter at finite temperature and in the regime where neutrinos are [...] Read more.
The integral parameters (mass, radius) of hot proto-quark stars that are formed in supernova explosion are studied. We use the MIT bag model to determine the pressure of up-down and strage quark matter at finite temperature and in the regime where neutrinos are trapped. It is shown that such stars are heated to temperatures of the order of tens of MeV. The maximum possible values of the central temperatures of these stars are determined. It is shown that the energy of neutrinos that are emitted from proto-quark stars is of the order of 250÷300 MeV. Once formed, the proto-quark stars cool by neutrino emission, which leads to a decrease in the mass of these stars by about 0.16–0.25 M for stars with the rest masses that are in the range Mb=1.221.62 M. Full article
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16 pages, 578 KiB  
Article
Equation of State of Strongly Magnetized Matter with Hyperons and Δ-Resonances
by Vivek Baruah Thapa, Monika Sinha, Jia Jie Li and Armen Sedrakian
Particles 2020, 3(4), 660-675; https://doi.org/10.3390/particles3040043 - 13 Oct 2020
Cited by 21 | Viewed by 2661
Abstract
We construct a new equation of state for the baryonic matter under an intense magnetic field within the framework of covariant density functional theory. The composition of matter includes hyperons as well as Δ-resonances. The extension of the nucleonic functional to the [...] Read more.
We construct a new equation of state for the baryonic matter under an intense magnetic field within the framework of covariant density functional theory. The composition of matter includes hyperons as well as Δ-resonances. The extension of the nucleonic functional to the hypernuclear sector is constrained by the experimental data on Λ and Ξ-hypernuclei. We find that the equation of state stiffens with the inclusion of the magnetic field, which increases the maximum mass of neutron star compared to the non-magnetic case. In addition, the strangeness fraction in the matter is enhanced. Several observables, like the Dirac effective mass, particle abundances, etc. show typical oscillatory behavior as a function of the magnetic field and/or density which is traced back to the occupation pattern of Landau levels. Full article
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9 pages, 624 KiB  
Article
A Bayesian Analysis on Neutron Stars within Relativistic Mean Field Models
by Prasanta Char, Silvia Traversi and Giuseppe Pagliara
Particles 2020, 3(3), 621-629; https://doi.org/10.3390/particles3030040 - 07 Aug 2020
Cited by 4 | Viewed by 2464
Abstract
We present a Bayesian analysis on the equation of state of neutron stars based on a class of relativistic mean field models. The priors on the equation of state are related to the properties of nuclear matter at saturation and the posteriors are [...] Read more.
We present a Bayesian analysis on the equation of state of neutron stars based on a class of relativistic mean field models. The priors on the equation of state are related to the properties of nuclear matter at saturation and the posteriors are obtained through the Bayesian procedure by exploiting recent astrophysical constraints on the mass–radius relations of neutron stars. We find indications of a tension (within the adopted model) between the prior on the nuclear incompressibility and its posterior which in turn seems to suggest a possible phase transition at about twice saturation density to a phase where the nucleon effective mass is strongly reduced. A possible relation with the chiral phase transition in dense matter is also discussed. Full article
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11 pages, 750 KiB  
Article
Neutron Stars in f(R)-Gravity and Its Extension with a Scalar Axion Field
by Artyom Astashenok and Sergey Odintsov
Particles 2020, 3(3), 532-542; https://doi.org/10.3390/particles3030036 - 01 Jul 2020
Cited by 5 | Viewed by 2452
Abstract
We present a brief review of general results about non-rotating neutron stars in simple R 2 gravity and its extension with a scalar axion field. Modified Einstein equations are presented for metrics in isotropical coordinates. The mass–radius relation, mass profile and dependence of [...] Read more.
We present a brief review of general results about non-rotating neutron stars in simple R 2 gravity and its extension with a scalar axion field. Modified Einstein equations are presented for metrics in isotropical coordinates. The mass–radius relation, mass profile and dependence of mass from central density on various equations of state are given in comparison to general relativity. Full article
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18 pages, 1038 KiB  
Article
Bulk Viscous Damping of Density Oscillations in Neutron Star Mergers
by Mark Alford, Arus Harutyunyan and Armen Sedrakian
Particles 2020, 3(2), 500-517; https://doi.org/10.3390/particles3020034 - 19 Jun 2020
Cited by 25 | Viewed by 2893
Abstract
In this paper, we discuss the damping of density oscillations in dense nuclear matter in the temperature range relevant to neutron star mergers. This damping is due to bulk viscosity arising from the weak interaction “Urca” processes of neutron decay and electron capture. [...] Read more.
In this paper, we discuss the damping of density oscillations in dense nuclear matter in the temperature range relevant to neutron star mergers. This damping is due to bulk viscosity arising from the weak interaction “Urca” processes of neutron decay and electron capture. The nuclear matter is modelled in the relativistic density functional approach. The bulk viscosity reaches a resonant maximum close to the neutrino trapping temperature, then drops rapidly as temperature rises into the range where neutrinos are trapped in neutron stars. We investigate the bulk viscous dissipation timescales in a post-merger object and identify regimes where these timescales are as short as the characteristic timescale ∼10 ms, and, therefore, might affect the evolution of the post-merger object. Our analysis indicates that bulk viscous damping would be important at not too high temperatures of the order of a few MeV and densities up to a few times saturation density. Full article
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16 pages, 4747 KiB  
Article
Astrophysics in the Laboratory—The CBM Experiment at FAIR
by Peter Senger
Particles 2020, 3(2), 320-335; https://doi.org/10.3390/particles3020024 - 02 Apr 2020
Cited by 5 | Viewed by 3059
Abstract
The future “Facility for Antiproton and Ion Research” (FAIR) is an accelerator-based international center for fundamental and applied research, which presently is under construction in Darmstadt, Germany. An important part of the program is devoted to questions related to astrophysics, including the origin [...] Read more.
The future “Facility for Antiproton and Ion Research” (FAIR) is an accelerator-based international center for fundamental and applied research, which presently is under construction in Darmstadt, Germany. An important part of the program is devoted to questions related to astrophysics, including the origin of elements in the universe and the properties of strongly interacting matter under extreme conditions, which are relevant for our understanding of the structure of neutron stars and the dynamics of supernova explosions and neutron star mergers. The Compressed Baryonic Matter (CBM) experiment at FAIR is designed to measure promising observables in high-energy heavy-ion collisions, which are expected to be sensitive to the high-density equation-of-state (EOS) of nuclear matter and to new phases of Quantum Chromo Dynamics (QCD) matter at high densities. The CBM physics program, the relevant observables and the experimental setup will be discussed. Full article
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12 pages, 1306 KiB  
Conference Report
Transport Properties in Magnetized Compact Stars
by Toshitaka Tatsumi and Hiroaki Abuki
Particles 2021, 4(1), 63-74; https://doi.org/10.3390/particles4010009 - 21 Feb 2021
Viewed by 1935
Abstract
Transport properties of dense quark matter are discussed in the strong magnetic field, B. B dependence as well as density dependence of the Hall conductivity is discussed, based on the microscopic Kubo formula. We took into account the possibility of the inhomogeneous [...] Read more.
Transport properties of dense quark matter are discussed in the strong magnetic field, B. B dependence as well as density dependence of the Hall conductivity is discussed, based on the microscopic Kubo formula. We took into account the possibility of the inhomogeneous chiral phase at moderate densities, where anomalous Hall effect is intrinsic and resembles the one in Weyl semimetals in condensed matter physics. Some theoretical aspects inherent in anomalous Hall effect are also discussed. Full article
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