HYPERON DENSITY DEPENDENCE OF HYPERON-NUCLEON INTERACTIONS IN NEUTRON STARS

2008 ◽  
Vol 17 (09) ◽  
pp. 1720-1728
Author(s):  
L. DANG ◽  
P. YUE ◽  
L. LI ◽  
P. Z. NING
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Density Dependence ◽  
Mean Field ◽  
Density Dependent ◽  
Effective Potentials ◽  
Relativistic Mean Field ◽  
Nucleon Interactions ◽  
Dependent Factor ◽  
Rmf Model

The hyperon density dependence (YDD) of hyperon-nucleon interactions are studied in the relativistic mean field (RMF) model and their influences on the properties of neutron stars are studied. The extended RMF considered the interior quarks coordinates of hyperon and bring a hyperon density dependent factor, f(ρY), to the meson-hyperon coupling vertexes. The hyperon density dependence of YN interaction affect the properties of neutron stars only after the corresponding hyperon appears. Then, the influences of the density dependence factors are almost ignored at low densities, which are clear at high densities. The compositions and properties of neutron stars are studied with and without the YDD of YN interactions for the different Σ--nucleus effective potentials, (30, 0, -30)MeV. The calculated results indicated that the YDD of YN interaction soften the equation of state of neutron stars at high densities.

THE INNER CRUST OF NEUTRON STARS IN RELATIVISTIC MEAN FIELD APPROACH

2008 ◽  
Vol 17 (09) ◽  
pp. 1765-1773 ◽  
Author(s):  
JIGUANG CAO ◽  
ZHONGYU MA ◽  
NGUYEN VAN GIAI
Keyword(s):  
Boundary Conditions ◽  
Neutron Stars ◽  
Mean Field ◽  
Bcs Theory ◽  
Neutron Density ◽  
Field Approach ◽  
Hartree Fock ◽  
Relativistic Mean Field ◽  
Density Distributions ◽  
Rmf Model

The microscopic properties and superfluidity of the inner crust in neutron stars are investigated in the framework of the relativistic mean field(RMF) model and BCS theory. The Wigner-Seitz(W-S) cell of inner crust is composed of neutron-rich nuclei immersed in a sea of dilute, homogeneous neutron gas. The pairing properties of nucleons in the W-S cells are treated in BCS theory with Gogny interaction. In this work, we emphasize on the choice of the boundary conditions in the RMF approach and superfluidity of the inner crust. Three kinds of boundary conditions are suggested. The properties of the W-S cells with the three kinds of boundary conditions are investigated. The neutron density distributions in the RMF and Hartree-Fock-Bogoliubov(HFB) models are compared.

EFFECTS OF Δ-BARYON INTERACTION STRENGTH ON NEUTRON STARS PROPERTIES

2007 ◽  
Vol 16 (02n03) ◽  
pp. 175-183 ◽  
Author(s):  
J. C. T. DE OLIVEIRA ◽  
S. B. DUARTE ◽  
H. RODRIGUES ◽  
M. CHIAPPARINI ◽  
M. KYOTOKU
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Mean Field Theory ◽  
Mean Field ◽  
Interaction Strength ◽  
Hadronic Matter ◽  
Resonance Neutron ◽  
Baryon Interaction ◽  
Relativistic Mean Field ◽  
Central Regions

We investigate the effect of Δ-resonance interaction strength on the equation of state of asymmetric hadronic matter and neutron stars structure. We discuss Δ-matter formation at high densities in the context of a relativistic mean field theory. We show that the attractive nature of the Δ-baryon interaction can induce a phase transition accompanying Δ-matter formation, at values of densities presumably existing in central regions of neutron stars. The possibility of a rich Δ-resonance neutron star is presented using the proposed equation of state.

HADRON-QUARK PHASE TRANSITION AND ANTIKAON CONDENSATION IN NEUTRON STARS

2008 ◽  
Vol 23 (27n30) ◽  
pp. 2481-2484
Author(s):  
H. SHEN ◽  
F. YANG ◽  
P. YUE
Keyword(s):  
Field Theory ◽  
Phase Transition ◽  
Equation Of State ◽  
Neutron Stars ◽  
Mean Field Theory ◽  
Mean Field ◽  
Maximum Mass ◽  
Relativistic Mean Field ◽  
The Core ◽  
Quark Phase

We study the hadron-quark phase transition and antikaon condensation which may occur in the core of massive neutron stars. The relativistic mean field theory is used to describe the hadronic phase, while the Nambu-Jona-Lasinio model is adopted for the quark phase. We find that the hadron-quark phase transition is very sensitive to the models used. The appearance of deconfined quark matter and antikaon condensation can soften the equation of state at high density and lower the maximum mass of neutron stars.

scholarly journals Relativistic Hartree Bogoliubov model with Density Dependent meson-nucleon couplings

2020 ◽  
Vol 15 ◽  
pp. 49
Author(s):  
G. A. Lalazissis ◽  
T. Niksic ◽  
D. Vretenar ◽  
P. Ring
Keyword(s):  
Density Dependence ◽  
Excited States ◽  
Effective Interaction ◽  
Mean Field ◽  
Ground States ◽  
Density Dependent ◽  
Relativistic Mean Field

A new improved relativistic mean-field effective interaction with explicit density dependence of the meson-nucleon couplings is proposed. The new effective interaction is called DD-ME2 and it is tested in Relativistic Hartree-Bogoliubov (RHB) and RPA calculations of nuclear ground-states and properties of excited states.

scholarly journals Mass correction and deformation of slowly rotating anisotropic neutron stars based on Hartle–Thorne formalism

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
M. L. Pattersons ◽  
A. Sulaksono
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Strong Field ◽  
Mean Field ◽  
Anisotropic Model ◽  
Relativistic Stars ◽  
Relativistic Mean Field ◽  
Mass Correction ◽  
The One ◽  
The Impact

AbstractDue to their compactness, neutron stars are the best study matter in high density and strong-field gravity. Hartle and Thorne have proposed a good approximation or perturbation procedure within general relativity for slowly rotating relativistic stars by assuming the matter inside the stars is an ideal isotropic fluid. This study extends the analytical Hartle–Thorne formalism for slowly rotating neutron stars, including the possibility that the neutron star pressure can be anisotropic. We study the impact of neutron stars’ anisotropy pressure on mass correction and deformation numerically. For the anisotropic model, we use the Bowers-Liang model. For the equation of state of neutron stars, we use a relativistic mean-field BSP parameter set with the hyperons, and for the crust equation of state, we use the one of Miyatsu et al. We have found that the mass of neutron stars increases but the radius decreases by increasing $$\lambda _{BL}$$ λ BL value. Therefore, the NS compactness increases when $$\lambda _{BL}$$ λ BL becomes larger. This fact leads to a condition in which NS is getting harder to deformed when the $$\lambda _{BL}$$ λ BL increased.

δ MESON EFFECTS ON ASYMMETRIC NUCLEAR MATTER

2008 ◽  
Vol 17 (09) ◽  
pp. 1815-1824 ◽  
Author(s):  
B. LIU ◽  
M. DI TORO ◽  
V. GRECO
Keyword(s):  
Neutron Stars ◽  
Nuclear Matter ◽  
Mean Field ◽  
Coupling Scheme ◽  
Asymmetric Nuclear Matter ◽  
Density Dependent ◽  
Remarkable Effect ◽  
Relativistic Mean Field ◽  
The Stability ◽  
The Impact

The impact of a δ meson field (the scalar-isovector channel) on asymmetric nuclear matter is studied within relativistic mean-field (RMF) models with both constant and density dependent (DD) nucleon-meson couplings. The Equation of State (EOS) for asymmetric nuclear matter and the neutron star properties by the different models are compared. We find that the δ-field in the constant coupling scheme leads to a larger repulsion in dense neutron-rich matter and to a definite splitting of proton and neutron effective masses, finally influencing the stability of the neutron stars. A broader analysis of possible δ-field effects is achieved considering also density dependent nucleon-meson coupling. A remarkable effect on the relation between mass and radius for the neutron stars is seen, showing a significant reduction of the radius along with a moderate mass reduction due to the increase of the effective δ coupling in high density regions.

scholarly journals Properties of rotating neutron star in density-dependent relativistic mean-field models

2020 ◽  
pp. 2150001
Author(s):  
Rashid Riahi ◽  
Seyed Zafarollah Kalantari
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Quadrupole Moment ◽  
Stability Region ◽  
Equations Of State ◽  
Mean Field ◽  
Low Frequency ◽  
Density Dependent ◽  
Relativistic Mean Field ◽  
Limit Value

Equilibrium sequences were developed for rotating neutron stars in the relativistic mean-field interaction framework using four density-dependent equations of state (EOSs) for the neutron star matter. These sequences were constructed for the observed rotation frequencies of 25, 317, 346, 716 and 1122[Formula: see text]Hz. The bounds of sequences, the secular axisymmetric instability, static and Keplerian sequences were calculated in each model to determine the stability region. The gravitational mass, quadrupole moment, polar, forward and backward redshifts, and Kerr parameter were calculated according to this stability region, and the allowable range of these quantities was then determined for each model. According to the results, DDF and DD-ME[Formula: see text] were unable to properly describe the low-frequency neutron stars, PSR J0348+432, PSR J1614-2230 and PSR J0740+6620 rotate at a frequency of 25, 317 and 346[Formula: see text]Hz, respectively. On the other hand, all the selected EOSs properly described the rotation of PSR J1748-244ad and PSR J1739-285 at a frequency of 716 and 1122[Formula: see text]Hz, respectively. The mass of these stars was, therefore, in the range of [Formula: see text] and [Formula: see text], respectively. The polar, forward and backward redshifts, and the quadrupole moment were calculated in all the selected rotating frequencies and the Keplerian sequence. The results were consistent with observations. Confirming the mass of [Formula: see text] for EXO 0748-676, our result, [Formula: see text], will be close to the observed value, and the EOSs used in this study properly describe this star. Interestingly, the extremum of Kerr parameter, polar, forward and backward redshifts in all models reached constant values of, [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], respectively. These behaviors of redshifts and Kerr parameter are approximately independent of EOS. The observed behaviors must evaluate by other EOSs to find universal relations for these quantities. Also, a limit value was found for each of these parameters. In this case where these parameters are greater than the limit value, the star can rotate at a frequency equal to or greater than [Formula: see text][Formula: see text]Hz.

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