NEUTRON STARS WITH PARAMETRIZED MESON COUPLINGS

2000 ◽  
Vol 15 (29) ◽  
pp. 1789-1800 ◽  
Author(s):  
A. R. TAURINES ◽  
C. A. Z. VASCONCELLOS ◽  
M. MALHEIRO ◽  
M. CHIAPPARINI
Keyword(s):  
Neutron Stars ◽  
Nuclear Matter ◽  
Degrees Of Freedom ◽  
Scalar Meson ◽  
Mean Field Theory ◽  
Mean Field ◽  
Static Properties ◽  
Relativistic Mean Field ◽  
Specific Choice

We investigate static properties of nuclear and neutron star matter by using a relativistic mean field theory with parametrized couplings. With a suitable choice of mathematical parameters, the couplings allow one to reproduce results of current quantum hadrodynamics models. For other parametrizations, a better description of bulk properties of nuclear matter is obtained. The formalism is extended to include hyperon and lepton degrees of freedom, and an analysis on the effects of the phenomenological couplings in the fermion populations and mass of neutron stars is performed. The results show a strong similarity between the predictions of ZM-like models and those with exponential couplings. We have observed in particular an extreme sensibility of the predictions of these theories on the specific choice of the values of the binding energy of nuclear matter and saturation density. Additionally, the role of the very intense scalar meson mean field found in the interior of neutron stars in the screening of the nucleon mass is discussed.

THE ROLE OF THE NUCLEAR MATTER COMPRESSION MODULUS IN NEUTRON STARS

2004 ◽  
Vol 13 (07) ◽  
pp. 1519-1524 ◽  
Author(s):  
VERÔNICA A. DEXHEIMER ◽  
CÉSAR A. Z. VASCONCELLOS ◽  
MOISÉS RAZEIRA ◽  
MANFRED DILLIG
Keyword(s):  
Neutron Stars ◽  
Nuclear Matter ◽  
Body Problem ◽  
Mean Field Theory ◽  
Mean Field ◽  
Compression Modulus ◽  
Baryon Number ◽  
Many Body ◽  
Relativistic Mean Field

For the nuclear many body problem at high densities, formulated in the framework of a relativistic mean-field theory, we investigate in detail the compression modulus of nuclear matter as a function of the effective nucleon mass. We include consistently in our modelling chemical equilibrium as well as baryon number and electric charge conservation and investigate properties of neutron stars. Among other predictions we focus on the dependence of the maximum mass of a sequence of neutron stars as a function of the compression modulus and the nucleon effective mass.

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.

A RELATIVISTIC MEAN FIELD THEORY FOR NUCLEAR MATTER AT T≠0

2004 ◽  
Vol 13 (07) ◽  
pp. 1177-1181
Author(s):  
ALEXANDRE MESQUITA ◽  
MOISÉS RAZEIRA ◽  
CÉSAR A. Z. VASCONCELLOS ◽  
MANFRED DILLIG ◽  
BARDO E. J. BODMANN
Keyword(s):  
Nuclear Matter ◽  
Mean Field Theory ◽  
Mean Field ◽  
Dense Matter ◽  
Baryon Number ◽  
Coupling Constants ◽  
Model Parameters ◽  
Static Properties ◽  
Relativistic Mean Field ◽  
Protoneutron Stars

We study effects of temperature in hadron dense matter within a generalized relativistic mean field approach based on the naturalness of the various coupling constants of the theory, The Lagrangian density of our formulation contains the fundamental baryon octet, nonlinear self-couplings of the σ and δ meson fields coupled to the baryons and to the ω and ρ meson fields. By adjusting the model parameters, after inclusion in a consistent way of chemical equilibrium, baryon number and electric charge conservation, our model describes static bulk properties of ordinary nuclear matter and neutron stars. In the framework of the Sommerfeld approximation, we extend our approach to the T≠0 domain. The Sommerfeld approximation allows a drastic simplification of computational work while improving the capability of the theoretical analysis of the role of temperature on static properties of protoneutron stars. We perform the calculations by using our nonlinear model, which we extend by considering trapped neutrinos introduced into the formalism by fixing the lepton fraction. Integrating the Tolman–Oppenheimer–Volkoff equations we have obtained standard plots for the mass and radius of protoneutron stars as a function of the central density and temperature. Our predictions include the determination of an absolute value for the protoneutron star limiting mass at low and intermediate temperature regimes.

NEUTRON STARS WITH KAON CONDENSATION IN RELATIVISTIC EFFECTIVE MODEL

2013 ◽  
Vol 22 (05) ◽  
pp. 1350026 ◽  
Author(s):  
CHEN WU ◽  
WEI-LIANG QIAN ◽  
YU-GANG MA ◽  
JI-FENG YANG
Keyword(s):  
Field Theory ◽  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Optical Potential ◽  
Mean Field Theory ◽  
Mean Field ◽  
Neutron Star Matter ◽  
Relativistic Mean Field ◽  
Kaon Condensation

Relativistic mean-field theory with parameter sets FSUGold and IU-FSU is extended to study the properties of neutron star matter in β equilibrium by including Kaon condensation. The mixed phase of normal baryons and Kaon condensation cannot exist in neutron star matter for the FSUGold model and the IU-FSU model. In addition, it is found that when the optical potential of the K- in normal nuclear matter UK ≳ -100 MeV , the Kaon condensation phase is absent in the inner cores of the neutron stars.

scholarly journals NUCLEAR MATTER IN INTENSE MAGNETIC FIELD AND WEAK PROCESSES

2001 ◽  
Vol 16 (03) ◽  
pp. 347-367 ◽  
Author(s):  
ASHOK GOYAL ◽  
V. K. GUPTA ◽  
KANUPRIYA GOSWAMI ◽  
VINITA TULI
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Magnetic Moments ◽  
Mean Field Theory ◽  
Mean Field ◽  
Hadronic Interactions ◽  
Relativistic Mean Field ◽  
Intense Magnetic Field ◽  
The Magnetic Field

We study the effect of magnetic field on the dominant neutrino emission processes in neutron stars. The processes are first calculated for the case when the magnetic field does not exceed the critical value to confine electrons to the lowest Landau state. We consider here magnetic fields up to ~1019 Gauss. We find that fields of strength 1015-1016 Gauss have significant effect on the neutronization process, for the direct URCA process the effect of the magnetic field becomes significant only at ~1019 Gauss. In order to estimate the effect we derive the composition of cold nuclear matter at high densities and in beta equilibrium, a situation appropriate for neutron stars. The hadronic interactions are incorporated through the exchange of scalar and vector mesons in the framework of relativistic mean field theory. In addition the effects of anomalous magnetic moments of nucleons are also considered.

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