Ryszard Manka

The role of nonlinear vector meson interactions in hyperon stars

An extended nonlinear model has been applied to construct a neutron star matter equation of state. In the case of neutron star matter with non-zero strangeness the extension of the vector meson sector by the inclusion of nonlinear mixed terms results in the stiffening of the equation of state and accordingly in the higher value of the maximum neutron star mass.

Properties of a protoneutron star in effective field theory

The complete form of the equation of state of strangeness rich protoneutron and neutron star matter has been obtained. The currently obtained lower value of the U{sub {lambda}}{sup ({lambda})} potential at the level of 5 MeV permits the existence of additional parameter set which reproduces the weaker {lambda}{lambda} interaction. The effects of the strength of hyperon-hyperon interactions on the equations of state constructed for the chosen parameter set have been analyzed. It has been shown that replacing the strong Y-Y interaction model by the weak one introduces large differences in the composition of a protoneutron star matter both in the strange and nonstrange sectors. Also concentrations of neutrinos have been significantly altered in protoneutron star interiors. The performed calculations have indicated that the change of the hyperon-hyperon coupling constants affects the value of the proto-neutron star maximum mass.

The influence of the strength of hyperon–hyperon interactions on neutron star properties

An equation of state of neutron star matter with strange baryons has been obtained. The effects of the strength of hyperon–hyperon interactions on the equations of state constructed for the chosen parameter sets have been analysed. Numerous neutron star models show that the appearance of hyperons is connected with the increasing density in neutron star interiors. The performed calculations have indicated that a change of the hyperon–hyperon coupling constants affects the chemical composition of a neutron star. The obtained numerical hyperon star models exclude a large population of strange baryons in the star interior.

Extended relativistic hyperon star model

In this paper an equation of state of neutron star matter, which includes strange baryons in the framework of Zimanyi and Moszkowski model has been obtained. We focus on the effects of the isospin dependence of the equation of state and construct the hyperon star model for the fitted parameters. Numerous neutron star models show that the appearance of hyperons is connected with the increasing density in neutron star interiors. Analysis carried out in this paper shows that the inclusion of

Theoretical model of a magnetic white dwarf

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Neutron star matter in a relativistic mean-field theory

meson and additional nonlinear meson interaction terms affects the density dependence of the symmetry energy and the chemical composition of a neutron star. Since the effective baryon masses contribute to baryon chemical potentials, they also alter the chemical composition of the star. The obtained model of the star not only excludes large population of hyperons but also does not significantly reduce the lepton content in the star interior.

The Quark strange star in the enlarged Nambu-Jona-Lasinio model

In this paper a theoretical model of a magnetic white dwarf is studied. All numerical calculations are performed under the assumption of a spherically symmetric star. The obtained equation of state is stiffer with the increase of value of the magnetic field (B). Numerical values of the maximum mass and radius are presented. The influence of the magnetic field on the results is evident. Finally the departure from the condition of isothermality of a degenerate electron gas in the gravitational field is discussed.

The Hot Neutron Star

The nucleon effective mass, binding energy, and neutron star configuration in the relativistic mean-field (RMF) theory are considered. The calculations are motivated by the construction of the equation of state for a neutron star in the RMF theory. The equations of state for different parameter sets are calculated using the Feynman-Bogoliubov variational method for temperature different from zero. Various equations of state enable the construction of neutron star models.

ON THE NEUTRINO BALL MODEL

The strange quark star is investigated within the enlarged SU(3) Nambu-Jona-Lasinio model. The stable quark star can exist until a maximal configuration with ρm = 3.1×1015xa0gxa0cm-3 with Mm = 1.61xa0M⊙ and Rm = 8.74xa0km is reached. Strange quarks appear for density above ρc = 9.84xa0gxa0cm-3 for the quark star with radius Rc = 8.003xa0km and Mc = 0.77 M⊙. A comparison of quark star properties obtained in the quark mean-field approach to a neutron star model constructed within the relativistic mean-field theory is presented.

The hyperon neutron star mean-field model

In this paper the equation of state of hot neutron matter is calculated. Involving the Oppenheimer-Volkov-Tolman equation global parameters of a neutron star at finite temperature are obtained.