Special Issue "Compact Stars in the QCD Phase Diagram"

A special issue of Universe (ISSN 2218-1997).

Deadline for manuscript submissions: closed (6 January 2018)

Special Issue Editors

Guest Editor
Prof. Dr. David Blaschke

1 Institute of Theoretical Physics, University of Wroclaw, 50-204 Wroclaw, Poland
2 Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
3 National Research Nuclear University (MEPhI), 115409 Moscow, Russia
Website | E-Mail
Guest Editor
Mr. Alexander Ayriyan

Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region, Russia
E-Mail
Guest Editor
Dr. Alexandra Friesen

Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region, Russia
E-Mail
Guest Editor
Dr. Hovik Grigorian

1 Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region, Russia
2 Yerevan State University, Alek Manyukyan 1, 0025 Yerevan, Republic of Armenia
E-Mail

Special Issue Information

Dear Colleagues,

This special issue is dedicated to the conference: Compact Stars in the QCD Phase Diagram VI http://theor.jinr.ru/~hmec16/csqcd6/.

This special issue will cover the following main topics:   

- QCD phase diagram for HIC vs. astrophysics   

- Quark deconfinement in HIC vs. supernovae, neutron stars and their mergers

- Strangeness in HIC and in compact stars   

- Equation of state and QCD phase transitions

Prof. Dr. David Blaschke
Dr. Hovik Grigorian
Mr. Alexander Ayriyan
Dr. Alexandra Friesen
Guest Editors

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 papers will be 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. Universe is an international peer-reviewed open access monthly 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 350 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 (18 papers)

View options order results:
result details:
Displaying articles 1-18
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessArticle Anomalous Electromagnetic Transport in Compact Stars
Universe 2018, 4(3), 54; doi:10.3390/universe4030054
Received: 9 January 2018 / Revised: 12 February 2018 / Accepted: 13 February 2018 / Published: 12 March 2018
Cited by 1 | PDF Full-text (745 KB) | HTML Full-text | XML Full-text
Abstract
We study the anomalous electromagnetic transport properties of a quark-matter phase that can be realized in the presence of a magnetic field in the low-temperature/moderate-high-density region of the Quantum Chromodynamics (QCD) phase map. In this so-called Magnetic Dual Chiral Density Wave phase, an
[...] Read more.
We study the anomalous electromagnetic transport properties of a quark-matter phase that can be realized in the presence of a magnetic field in the low-temperature/moderate-high-density region of the Quantum Chromodynamics (QCD) phase map. In this so-called Magnetic Dual Chiral Density Wave phase, an inhomogeneous condensate is dynamically induced producing a nontrivial topology, a consequence of the asymmetry of the lowest Landau level modes of the quasiparticles in this phase. The nontrivial topology manifests in the electromagnetic effective action via a chiral anomaly term θ F μ ν F ˜ μ ν , with an axion field θ given by the phase of the Dual Chiral Density Wave condensate. The coupling of the axion with the electromagnetic field leads to several macroscopic effects that include, among others, an anomalous, nondissipative Hall current, an anomalous electric charge, magnetoelectricity, and the formation of a hybridized propagating mode known as an axion polariton. The possible existence of this phase in the inner core of neutron stars opens a window to search for signals of its anomalous transport properties. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Open AccessArticle Non-Radial Oscillation Modes of Superfluid Neutron Stars Modeled with CompOSE
Universe 2018, 4(3), 53; doi:10.3390/universe4030053
Received: 16 January 2018 / Revised: 15 February 2018 / Accepted: 24 February 2018 / Published: 9 March 2018
PDF Full-text (392 KB) | HTML Full-text | XML Full-text
Abstract
We compute the principal non-radial oscillation mode frequencies of Neutron Stars described with a Skyrme-like Equation of State (EoS), taking into account the possibility of neutron and proton superfluidity. Using the CompOSE database and interpolation routines to obtain the needed thermodynamic quantities, we
[...] Read more.
We compute the principal non-radial oscillation mode frequencies of Neutron Stars described with a Skyrme-like Equation of State (EoS), taking into account the possibility of neutron and proton superfluidity. Using the CompOSE database and interpolation routines to obtain the needed thermodynamic quantities, we solve the fluid oscillation equations numerically in the background of a fully relativistic star, and identify imprints of the superfluid state. Though these modes cannot be observed with current technology, increased sensitivity of future Gravitational-Wave Observatories could allow us to observe these oscillations and potentially constrain or refine models of dense matter relevant to the interior of neutron stars. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessArticle Looking for the Phase Transition—Recent NA61/SHINE Results
Universe 2018, 4(3), 52; doi:10.3390/universe4030052
Received: 16 January 2018 / Revised: 13 February 2018 / Accepted: 19 February 2018 / Published: 9 March 2018
PDF Full-text (3004 KB) | HTML Full-text | XML Full-text
Abstract
The fixed-target NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) seeks to find the critical point (CR) of strongly interacting matter as well as the properties of the onset of deconfinement. The experiment provides a scan of measurements of particle spectra and
[...] Read more.
The fixed-target NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) seeks to find the critical point (CR) of strongly interacting matter as well as the properties of the onset of deconfinement. The experiment provides a scan of measurements of particle spectra and fluctuations in proton–proton, proton–nucleus, and nucleus–nucleus interactions as functions of collision energy and system size, corresponding to a two-dimensional phase diagram (T- μ B ). New NA61/SHINE results are shown here, including transverse momentum and multiplicity fluctuations in Ar+Sc collisions as compared to NA61 p+p and Be+Be data, as well earlier NA49 A+A results. Recently, a preliminary effect of change in the system size dependence, labelled as the “percolation threshold” or the “onset of fireball”, was observed in NA61/SHINE data. This effect is closely related to the vicinity of the hadronic phase space transition region and will be discussed in the text. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessCommunication Hadron–Quark Combustion as a Nonlinear, Dynamical System
Universe 2018, 4(3), 51; doi:10.3390/universe4030051
Received: 17 January 2018 / Revised: 1 March 2018 / Accepted: 2 March 2018 / Published: 7 March 2018
PDF Full-text (740 KB) | HTML Full-text | XML Full-text
Abstract
The hadron–quark combustion front is a system that couples various processes, such as chemical reactions, hydrodynamics, diffusion, and neutrino transport. Previous numerical work has shown that this system is very nonlinear, and can be very sensitive to some of these processes. In these
[...] Read more.
The hadron–quark combustion front is a system that couples various processes, such as chemical reactions, hydrodynamics, diffusion, and neutrino transport. Previous numerical work has shown that this system is very nonlinear, and can be very sensitive to some of these processes. In these proceedings, we contextualize the hadron–quark combustion as a nonlinear system, subject to dramatic feedback triggered by leptonic weak decays and neutrino transport. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessArticle Rotating Quark Stars in General Relativity
Universe 2018, 4(3), 48; doi:10.3390/universe4030048
Received: 4 January 2018 / Revised: 23 February 2018 / Accepted: 26 February 2018 / Published: 5 March 2018
PDF Full-text (384 KB) | HTML Full-text | XML Full-text
Abstract
We have built quasi-equilibrium models for uniformly rotating quark stars in general relativity. The conformal flatness approximation is employed and the Compact Object CALculator (cocal) code is extended to treat rotating stars with surface density discontinuity. In addition to the widely
[...] Read more.
We have built quasi-equilibrium models for uniformly rotating quark stars in general relativity. The conformal flatness approximation is employed and the Compact Object CALculator (cocal) code is extended to treat rotating stars with surface density discontinuity. In addition to the widely used MIT bag model, we have considered a strangeon star equation of state (EoS), suggested by Lai and Xu, that is based on quark clustering and results in a stiff EoS. We have investigated the maximum mass of uniformly rotating axisymmetric quark stars. We have also built triaxially deformed solutions for extremely fast rotating quark stars and studied the possible gravitational wave emission from such configurations. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessArticle Many Aspects of Magnetic Fields in Neutron Stars
Universe 2018, 4(3), 43; doi:10.3390/universe4030043
Received: 11 December 2017 / Revised: 25 January 2018 / Accepted: 7 February 2018 / Published: 26 February 2018
PDF Full-text (3430 KB) | HTML Full-text | XML Full-text
Abstract
In this work, we explore different aspects in which strong magnetic fields play a role in the composition, structure and evolution of neutron stars. More specifically, we discuss (i) how strong magnetic fields change the equation of state of dense matter, alter its
[...] Read more.
In this work, we explore different aspects in which strong magnetic fields play a role in the composition, structure and evolution of neutron stars. More specifically, we discuss (i) how strong magnetic fields change the equation of state of dense matter, alter its composition, and create anisotropies, (ii) how they change the structure of neutron stars (such mass and radius) and the formalism necessary to calculate those changes, and (iii) how they can affect neutron stars’ evolution. In particular, we focus on how a time-dependent magnetic field modifies the cooling of a special group known as X-ray dim neutron stars. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessArticle QCD Equations of State in Hadron–Quark Continuity
Universe 2018, 4(2), 42; doi:10.3390/universe4020042
Received: 3 January 2018 / Revised: 12 February 2018 / Accepted: 13 February 2018 / Published: 19 February 2018
PDF Full-text (2362 KB) | HTML Full-text | XML Full-text
Abstract
The properties of dense matter in quantum chromodynamics (QCD) are delineated through equations of state constrained by the neutron star observations. The two solar mass constraint, the radius constraint of ≃11–13 km, and the causality constraint on the speed of sound, are used
[...] Read more.
The properties of dense matter in quantum chromodynamics (QCD) are delineated through equations of state constrained by the neutron star observations. The two solar mass constraint, the radius constraint of ≃11–13 km, and the causality constraint on the speed of sound, are used to develop the picture of hadron–quark continuity in which hadronic matter continuously transforms into quark matter. A unified equation of state at zero temperature and β-equilibrium is constructed by a phenomenological interpolation between nuclear and quark matter equations of state. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessArticle Prospects of Constraining the Dense Matter Equation of State from Timing Analysis of Pulsars in Double Neutron Star Binaries: The Cases of PSR J0737 ‒ 3039A and PSR J1757 ‒ 1854
Universe 2018, 4(2), 36; doi:10.3390/universe4020036
Received: 4 December 2017 / Revised: 8 February 2018 / Accepted: 8 February 2018 / Published: 12 February 2018
PDF Full-text (638 KB) | HTML Full-text | XML Full-text
Abstract
The Lense-Thirring effect from spinning neutron stars in double neutron star binaries contributes to the periastron advance of the orbit. This extra term involves the moment of inertia of the neutron stars. The moment of inertia, on the other hand, depends on the
[...] Read more.
The Lense-Thirring effect from spinning neutron stars in double neutron star binaries contributes to the periastron advance of the orbit. This extra term involves the moment of inertia of the neutron stars. The moment of inertia, on the other hand, depends on the mass and spin of the neutron star, as well as the equation of state of the matter. If at least one member of the double neutron star binary (better the faster one) is a radio pulsar, then accurate timing analysis might lead to the estimation of the contribution of the Lense-Thirring effect to the periastron advance, which will lead to the measurement of the moment of inertia of the pulsar. The combination of the knowledge on the values of the moment of inertia, the mass and the spin of the pulsar will give a new constraint on the equation of state. Pulsars in double neutron star binaries are the best for this purpose as short orbits and moderately high eccentricities make the Lense-Thirring effect substantial, whereas tidal effects are negligible (unlike pulsars with main sequence or white-dwarf binaries). The most promising pulsars are PSR J0737 − 3039A and PSR J1757 − 1854. The spin-precession of pulsars due to the misalignment between the spin and the orbital angular momentum vectors affect the contribution of the Lense-Thirring effect to the periastron advance. This effect has been explored for both PSR J0737 − 3039A and PSR J1757 − 1854, and as the misalignment angles for both of these pulsars are small, the variation in the Lense-Thirring term is not much. However, to extract the Lense-Thirring effect from the observed rate of the periastron advance, more accurate timing solutions including precise proper motion and distance measurements are essential. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessFeature PaperArticle A Phenomenological Equation of State of Strongly Interacting Matter with First-Order Phase Transitions and Critical Points
Universe 2018, 4(2), 32; doi:10.3390/universe4020032
Received: 12 December 2017 / Revised: 8 January 2018 / Accepted: 29 January 2018 / Published: 9 February 2018
Cited by 1 | PDF Full-text (262 KB) | HTML Full-text | XML Full-text
Abstract
An extension of the relativistic density functional approach to the equation of state for strongly interacting matter is suggested that generalizes a recently developed modified excluded-volume mechanism to the case of temperature- and density-dependent available-volume fractions. A parametrization of this dependence is presented
[...] Read more.
An extension of the relativistic density functional approach to the equation of state for strongly interacting matter is suggested that generalizes a recently developed modified excluded-volume mechanism to the case of temperature- and density-dependent available-volume fractions. A parametrization of this dependence is presented for which, at low temperatures and suprasaturation densities, a first-order phase transition is obtained. It changes for increasing temperatures to a crossover transition via a critical endpoint. This provides a benchmark case for studies of the role of such a point in hydrodynamic simulations of ultrarelativistic heavy-ion collisions. The approach is thermodynamically consistent and extendable to finite isospin asymmetries that are relevant for simulations of neutron stars, their mergers, and core-collapse supernova explosions. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessArticle Vector-Interaction-Enhanced Bag Model
Universe 2018, 4(2), 30; doi:10.3390/universe4020030
Received: 4 December 2017 / Revised: 23 January 2018 / Accepted: 24 January 2018 / Published: 8 February 2018
PDF Full-text (392 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A commonly applied quark matter model in astrophysics is the thermodynamic bag model (tdBAG). The original MIT bag model approximates the effect of quark confinement, but does not explicitly account for the breaking of chiral symmetry, an important property of Quantum Chromodynamics (QCD).
[...] Read more.
A commonly applied quark matter model in astrophysics is the thermodynamic bag model (tdBAG). The original MIT bag model approximates the effect of quark confinement, but does not explicitly account for the breaking of chiral symmetry, an important property of Quantum Chromodynamics (QCD). It further ignores vector repulsion. The vector-interaction-enhanced bag model (vBag) improves the tdBAG approach by accounting for both dynamical chiral symmetry breaking and repulsive vector interactions. The latter is of particular importance to studies of dense matter in beta-equilibriumto explain the two solar mass maximum mass constraint for neutron stars. The model is motivated by analyses of QCD based Dyson-Schwinger equations (DSE), assuming a simple quark-quark contact interaction. Here, we focus on the study of hybrid neutron star properties resulting from the application of vBag and will discuss possible extensions. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessArticle On Cooling of Neutron Stars with a Stiff Equation of State Including Hyperons
Universe 2018, 4(2), 29; doi:10.3390/universe4020029
Received: 29 November 2017 / Revised: 14 January 2018 / Accepted: 15 January 2018 / Published: 8 February 2018
PDF Full-text (847 KB) | HTML Full-text | XML Full-text
Abstract
Exploiting a stiff equation of state of the relativistic mean-field model MKVORHϕ with σ-scaled hadron effective masses and couplings, including hyperons, we demonstrate that the existing neutron-star cooling data can be appropriately described within “the nuclear medium cooling scenario” under the
[...] Read more.
Exploiting a stiff equation of state of the relativistic mean-field model MKVORH ϕ with σ -scaled hadron effective masses and couplings, including hyperons, we demonstrate that the existing neutron-star cooling data can be appropriately described within “the nuclear medium cooling scenario” under the assumption that different sources have different masses. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Review

Jump to: Research, Other

Open AccessReview The Merger of Two Compact Stars: A Tool for Dense Matter Nuclear Physics
Universe 2018, 4(3), 50; doi:10.3390/universe4030050
Received: 1 February 2018 / Revised: 19 February 2018 / Accepted: 20 February 2018 / Published: 7 March 2018
PDF Full-text (266 KB) | HTML Full-text | XML Full-text
Abstract
We discuss the different signals, in gravitational and electromagnetic waves, emitted during the merger of two compact stars. We will focus in particular on the possible contraints that those signals can provide on the equation of state of dense matter. Indeed, the stiffness
[...] Read more.
We discuss the different signals, in gravitational and electromagnetic waves, emitted during the merger of two compact stars. We will focus in particular on the possible contraints that those signals can provide on the equation of state of dense matter. Indeed, the stiffness of the equation of state and the particle composition of the merging compact stars strongly affect, e.g., the life time of the post-merger remnant and its gravitational wave signal, the emission of the short gamma-ray-burst, the amount of ejected mass and the related kilonova. The first detection of gravitational waves from the merger of two compact stars in August 2017, GW170817, and the subsequent detections of its electromagnetic counterparts, GRB170817A and AT2017gfo, is the first example of the era of “multi-messenger astronomy”: we discuss what we have learned from this detection on the equation of state of compact stars and we provide a tentative interpretation of this event, within the two families scenario, as being due to the merger of a hadronic star with a quark star. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)

Other

Jump to: Research, Review

Open AccessConference Report Equation of State for Dense Matter with a QCD Phase Transition
Universe 2018, 4(3), 45; doi:10.3390/universe4030045
Received: 14 January 2018 / Revised: 21 February 2018 / Accepted: 21 February 2018 / Published: 1 March 2018
PDF Full-text (1000 KB) | HTML Full-text | XML Full-text
Abstract
We construct a dense matter equation of state (EoS) starting from a hadronic density dependent relativistic mean-field model with a DD2 parametrization including the excluded volume corrections at low densities. The high density part is given by a Nambu–Jona–Lasinio (NJL) model with multi-quark
[...] Read more.
We construct a dense matter equation of state (EoS) starting from a hadronic density dependent relativistic mean-field model with a DD2 parametrization including the excluded volume corrections at low densities. The high density part is given by a Nambu–Jona–Lasinio (NJL) model with multi-quark interactions. This EoS is characterized by increasing speed of sound below and above the phase transition region. The first order transition region has a large latent heat leaving a distinctive signature in the mass-radii relations in terms of twin stars. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessConference Report Cracking Strange Stars by Torsional Oscillations
Universe 2018, 4(2), 41; doi:10.3390/universe4020041
Received: 8 December 2017 / Revised: 19 January 2018 / Accepted: 29 January 2018 / Published: 17 February 2018
PDF Full-text (985 KB) | HTML Full-text | XML Full-text
Abstract
Strange stars are one of the possible compact stellar objects formed in the core collapse of supernovae. These hypothetical stars are made by deconfined quark matter and are selfbound. In our study, we focus on the torsional oscillations of a non bare strange
[...] Read more.
Strange stars are one of the possible compact stellar objects formed in the core collapse of supernovae. These hypothetical stars are made by deconfined quark matter and are selfbound. In our study, we focus on the torsional oscillations of a non bare strange star, i.e., a strange star with a thin crust made of standard nuclear matter. We construct a theoretical model assuming that the inner parts of the star are in two different phases, namely the color flavour locked phase and the crystalline colour superconducting phase. Since the latter phase is rigid, with a large shear modulus, it corresponds to a first stellar crust. Above this crust a second small crust made by standard nuclear matter is suspended thanks to a strong electromagnetic dipolar moment. We focus on the electromagnetically coupled oscillations of the two stellar crusts. Notably, we find that if a small fraction of the energy of a glitch event like a typical Vela glitch is conveyed in torsional oscillations, the small nuclear crust will likely break. This is due to the fact that in this model the maximum stress, due to torsional oscillations, is likely located near the star surface. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessConference Report Strangeness Production in Nucleus-Nucleus Collisions at SIS Energies
Universe 2018, 4(2), 37; doi:10.3390/universe4020037
Received: 30 November 2017 / Revised: 8 January 2018 / Accepted: 15 January 2018 / Published: 13 February 2018
PDF Full-text (308 KB) | HTML Full-text | XML Full-text
Abstract
Simulating Many Accelerated Strongly-interacting Hadrons (SMASH) is a new hadronic transport approach designed to describe the non-equilibrium evolution of heavy-ion collisions. The production of strange particles in such systems is enhanced compared to elementary reactions (Blume and Markert 2011), providing an interesting signal
[...] Read more.
Simulating Many Accelerated Strongly-interacting Hadrons (SMASH) is a new hadronic transport approach designed to describe the non-equilibrium evolution of heavy-ion collisions. The production of strange particles in such systems is enhanced compared to elementary reactions (Blume and Markert 2011), providing an interesting signal to study. Two different strangeness production mechanisms are discussed: one based on resonances and another using forced canonical thermalization. Comparisons to experimental data from elementary collisions are shown. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessConference Report From Heavy-Ion Collisions to Compact Stars: Equation of State and Relevance of the System Size
Universe 2018, 4(1), 14; doi:10.3390/universe4010014
Received: 30 November 2017 / Revised: 11 January 2018 / Accepted: 16 January 2018 / Published: 23 January 2018
PDF Full-text (3263 KB) | HTML Full-text | XML Full-text
Abstract
In this article, we start by presenting state-of-the-art methods allowing us to compute moments related to the globally conserved baryon number, by means of first principle resummed perturbative frameworks. We focus on such quantities for they convey important properties of the finite temperature
[...] Read more.
In this article, we start by presenting state-of-the-art methods allowing us to compute moments related to the globally conserved baryon number, by means of first principle resummed perturbative frameworks. We focus on such quantities for they convey important properties of the finite temperature and density equation of state, being particularly sensitive to changes in the degrees of freedom across the quark-hadron phase transition. We thus present various number susceptibilities along with the corresponding results as obtained by lattice quantum chromodynamics collaborations, and comment on their comparison. Next, omitting the importance of coupling corrections and considering a zero-density toy model for the sake of argument, we focus on corrections due to the small size of heavy-ion collision systems, by means of spatial compactifications. Briefly motivating the relevance of finite size effects in heavy-ion physics, in opposition to the compact star physics, we present a few preliminary thermodynamic results together with the speed of sound for certain finite size relativistic quantum systems at very high temperature. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessConference Report Charged ρ Meson Condensate in Neutron Stars within RMF Models
Universe 2018, 4(1), 1; doi:10.3390/universe4010001
Received: 30 November 2017 / Revised: 12 December 2017 / Accepted: 12 December 2017 / Published: 26 December 2017
PDF Full-text (405 KB) | HTML Full-text | XML Full-text
Abstract
Knowledge of the equation of state (EoS) of cold and dense baryonic matter is essential for the description of properties of neutron stars (NSs). With an increase of the density, new baryon species can appear in NS matter, as well as various meson
[...] Read more.
Knowledge of the equation of state (EoS) of cold and dense baryonic matter is essential for the description of properties of neutron stars (NSs). With an increase of the density, new baryon species can appear in NS matter, as well as various meson condensates. In previous works, we developed relativistic mean-field (RMF) models with hyperons and Δ -isobars, which passed the majority of known experimental constraints, including the existence of a 2 M neutron star. In this contribution, we present results of the inclusion of ρ -meson condensation into these models. We have shown that, in one class of the models (so-called KVOR-based models, in which the additional stiffening procedure is introduced in the isoscalar sector), the condensation gives only a small contribution to the EoS. In another class of the models (MKVOR-based models with additional stiffening in isovector sector), the condensation can lead to a first-order phase transition and a substantial decrease of the NS mass. Nevertheless, in all resulting models, the condensation does not spoil the description of the experimental constraints. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Open AccessConference Report Directed Flow in Heavy-Ion Collisions and Its Implications for Astrophysics
Universe 2017, 3(4), 79; doi:10.3390/universe3040079
Received: 17 October 2017 / Revised: 6 November 2017 / Accepted: 7 November 2017 / Published: 14 November 2017
PDF Full-text (287 KB) | HTML Full-text | XML Full-text
Abstract
Analysis of directed flow (v1) of protons, antiprotons and pions in heavy-ion collisions is performed in the range of collision energies sNN = 2.7–39 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation
[...] Read more.
Analysis of directed flow ( v 1 ) of protons, antiprotons and pions in heavy-ion collisions is performed in the range of collision energies s N N = 2.7–39 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS with deconfinement transitions: a first-order phase transition and a smooth crossover transition. The crossover EoS is unambiguously preferable for the description of experimental data at lower collision energies s N N 20 Gev. However, at higher collision energies s N N 20 Gev. the purely hadronic EoS again becomes advantageous. This indicates that the deconfinement EoS in the quark-gluon sector should be stiffer at high baryon densities than those used in the calculation. The latter finding is in agreement with that discussed in astrophysics in connection with existence of hybrid stars with masses up to about two solar masses. Full article
(This article belongs to the Special Issue Compact Stars in the QCD Phase Diagram)
Figures

Figure 1

Back to Top