scholarly journals δ MESON EFFECTS ON NEUTRON STARS IN THE MODIFIED QUARK–MESON COUPLING MODEL

2010 ◽  
Vol 19 (11) ◽  
pp. 2247-2263 ◽  
Author(s):  
ZHONG-MING NIU ◽  
CHUN-YUAN GAO
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Coupling Model ◽  
Considerable Change ◽  
Hadronic Matter ◽  
Maximum Mass ◽  
Meson Field ◽  
Meson Coupling

The properties of neutron stars are investigated by including δ meson field in the modified quark–meson coupling model. It is found that δ meson has opposite effects on hadronic matter with or without hyperons: it softens the EOSs of hadronic matter with hyperons, while it stiffens the EOSs of pure nucleonic matter. Moreover, by replacing the isovector mesons with the contact scalar–isovector interaction, a considerable change of proton fraction is observed. It is shown that the contact scalar–isovector interaction provides an approach to satisfy the constraint of Direct Urca critical star masses. However, the inclusion of δ meson increases the proton fraction, consequently it decreases the M DU which departs farther from the Direct Urca constraint. Furthermore, the inclusion of δ meson field can increase the maximum mass of neutron star and enlarge the corresponding radius, while these quantities are decreased when the contact scalar–isovector interaction is included.

scholarly journals Contraction of cold neutron star due to in the presence a quark core

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
B. Eslam Panah ◽  
T. Yazdizadeh ◽  
G. H. Bordbar
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Quark Matter ◽  
Average Density ◽  
Dynamical Stability ◽  
Hadronic Matter ◽  
Maximum Mass ◽  
Quark Core ◽  
Hybrid Stars ◽  
Schwarzschild Radius

Abstract Motivated by importance of the existence of quark matter on structure of neutron star. For this purpose, we use a suitable equation of state (EoS) which include three different parts: (i) a layer of hadronic matter, (ii) a mixed phase of quarks and hadrons, and, (iii) a strange quark matter in the core. For this system, in order to do more investigation of the EoS, we evaluate energy, Le Chatelier’s principle and stability conditions. Our results show that the EoS satisfies these conditions. Considering this EoS, we study the effect of quark matter on the structure of neutron stars such as maximum mass and the corresponding radius, average density, compactness, Kretschmann scalar, Schwarzschild radius, gravitational redshift and dynamical stability. Also, considering the mentioned EoS in this paper, we find that the maximum mass of hybrid stars is a little smaller than that of the corresponding pure neutron star. Indeed the maximum mass of hybrid stars can be quite close to the pure neutron stars. Our calculations about the dynamical stability show that these stars are stable against the radial adiabatic infinitesimal perturbations. In addition, our analyze indicates that neutron stars are under a contraction due to the existence of quark core.

THE EFFECT OF THE SCALAR-ISOVECTOR MESON FIELD ON HYPERON-RICH NEUTRON STAR MATTER

2008 ◽  
Vol 17 (07) ◽  
pp. 1293-1307 ◽  
Author(s):  
AI-JUN MI ◽  
WEI ZUO ◽  
ANG LI
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Mean Field Theory ◽  
Mean Field ◽  
Maximum Mass ◽  
Meson Field ◽  
Neutron Star Matter ◽  
Relativistic Mean Field ◽  
Strangeness Content ◽  
Positively Charged

We investigate the effect of the scalar-isovector δ-meson field on the equation of state (EOS) and composition of hyperonic neutron star matter, and the properties of hyperonic neutron stars within the framework of the relativistic mean field theory. The influence of the δ-field turns out to be quite different and generally weaker for hyperonic neutron star matter as compared to that for npeμ neutron star matter. We find that inclusion of the δ-field enhances the strangeness content slightly and consequently moderately softens the EOS of neutron star matter in its hyperonic phase. As for the composition of hyperonic star matter, the effect of the δ-field is shown to shift the onset of the negatively-charged (positively-charged) hyperons to slightly lower (higher) densities and to enhance (reduce) their abundances. The influence of the δ-field on the maximum mass of hyperonic neutron stars is found to be fairly weak, whereas inclusion of the δ-field turns out to enhance sizably both the radii and the moments of inertia of neutron stars with given masses. It is also shown that the effects of the δ-field on the properties of hyperonic neutron stars remain similar in the case of switching off the Σ hyperons.

scholarly journals Neutron stars within the Bogoliubov quark-meson coupling model

2021 ◽  
Vol 103 (3) ◽  
Author(s):  
Aziz Rabhi ◽  
Constança Providência ◽  
Steven A. Moszkowski ◽  
João da Providência ◽  
Henrik Bohr
Keyword(s):  
Neutron Stars ◽  
Coupling Model ◽  
Meson Coupling

scholarly journals Astrophysical implications of neutron star inspiral and coalescence

2020 ◽  
Vol 29 (11) ◽  
pp. 2041015
Author(s):  
John L. Friedman ◽  
Nikolaos Stergioulas
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Maximum Mass ◽  
X Ray ◽  
Spectral Bands ◽  
Heaviest Elements ◽  
X Ray Binaries

The first inspiral of two neutron stars observed in gravitational waves was remarkably close, allowing the kind of simultaneous gravitational wave and electromagnetic observation that had not been expected for several years. Their merger, followed by a gamma-ray burst and a kilonova, was observed across the spectral bands of electromagnetic telescopes. These GW and electromagnetic observations have led to dramatic advances in understanding short gamma-ray bursts; determining the origin of the heaviest elements; and determining the maximum mass of neutron stars. From the imprint of tides on the gravitational waveforms and from observations of X-ray binaries, one can extract the radius and deformability of inspiraling neutron stars. Together, the radius, maximum mass, and causality constrain the neutron-star equation of state, and future constraints can come from observations of post-merger oscillations. We selectively review these results, filling in some of the physics with derivations and estimates.

scholarly journals Fundamental physics and the absence of sub-millisecond pulsars

2018 ◽  
Vol 620 ◽  
pp. A69 ◽  
Author(s):  
B. Haskell ◽  
J. L. Zdunik ◽  
M. Fortin ◽  
M. Bejger ◽  
R. Wijnands ◽  
...  
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Equations Of State ◽  
Rotation Frequency ◽  
Hadronic Matter ◽  
Spin Distribution ◽  
Test Models ◽  
State Of Matter

Context. Rapidly rotating neutron stars are an ideal laboratory to test models of matter at high densities. In particular, the maximum rotation frequency of a neutron star depends on the equation of state and can be used to test models of the interior. However, observations of the spin distribution of rapidly rotating neutron stars show evidence for a lack of stars spinning at frequencies higher than f ≈ 700 Hz, well below the predictions of theoretical equations of state. This has generally been taken as evidence of an additional spin-down torque operating in these systems, and it has been suggested that gravitational wave torques may be operating and be linked to a potentially observable signal. Aims. We aim to determine whether additional spin-down torques (possibly due to gravitational wave emission) are necessary, or if the observed limit of f ≈ 700 Hz could correspond to the Keplerian (mass-shedding) break-up frequency for the observed systems, and is simply a consequence of the currently unknown state of matter at high densities. Methods. Given our ignorance with regard to the true equation of state of matter above nuclear saturation densities, we make a minimal physical assumption and only demand causality, that is, that the speed of sound in the interior of the neutron star should be lower than or equal to the speed of light c. We then connected our causally limited equation of state to a realistic microphysical crustal equation of state for densities below nuclear saturation density. This produced a limiting model that gave the lowest possible maximum frequency, which we compared to observational constraints on neutron star masses and frequencies. We also compared our findings with the constraints on the tidal deformability obtained in the observations of the GW170817 event. Results. We rule out centrifugal breakup as the mechanism preventing pulsars from spinning faster than f ≈ 700 Hz, as the lowest breakup frequency allowed by our causal equation of state is f ≈ 1200 Hz. A low-frequency cutoff, around f ≈ 800 Hz could only be possible when we assume that these systems do not contain neutron stars with masses above M ≈ 2 M⊙. This would have to be due either to selection effects, or possibly to a phase transition in the interior of the neutron star that leads to softening at high densities and a collapse to either a black hole or a hybrid star above M ≈ 2 M⊙. Such a scenario would, however, require a somewhat unrealistically stiff equation of state for hadronic matter, in tension with recent constraints obtained from gravitational wave observations of a neutron star merger.

scholarly journals Quark-meson coupling model, nuclear matter constraints, and neutron star properties

2014 ◽  
Vol 89 (6) ◽  
Author(s):  
D. L. Whittenbury ◽  
J. D. Carroll ◽  
A. W. Thomas ◽  
K. Tsushima ◽  
J. R. Stone
Keyword(s):  
Neutron Star ◽  
Nuclear Matter ◽  
Coupling Model ◽  
Meson Coupling

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.

Strange hadronic matter in a modified quark-meson coupling model

1999 ◽  
Vol 653 (2) ◽  
pp. 166-184 ◽  
Author(s):  
P. Wang ◽  
R.K. Su ◽  
H.Q. Song ◽  
L.L. Zhang
Keyword(s):  
Coupling Model ◽  
Hadronic Matter ◽  
Meson Coupling
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