Narrow Results

The properties of rotating quark star are studied using the equation of state obtained from chiral colour dielectric model. The results are compared with those obtained from MIT bag model equation of state. The frequencies in the corotating innermost circular orbits for different central densities are evaluated and compared with the observed data.

We develop statistical mechanics and thermodynamics of Bose and Fermi systems in relativistic harmonic oscillator (RHO) confining potential, which is applicable in quark gluon plasma (QGP), astrophysics, Bose–Einstein condensation (BEC) etc. Detailed study of QGP system is carried out and compared with lattice results. Furthermore, as an application, our equation of state (EoS) of QGP is used to study compact stars like quark star.

The relativistic harmonic oscillator (RHO) model of hadrons is used to study quark stars. The mass–radius relationship is obtained and compared with bag model of quark star, using Tolman–Oppenheimer–Volkoff equation. In this model, the outward degenerate pressure due to discrete Landau levels and Landau degeneracy balances the inward gravitational pressure. Where as in bag model the degenerate pressure is due to the standard continuum levels which balances the combined inward pressure due to gravitation and bag pressure. So in RHO model, the confinement effect is included in the degenerate pressure. We found a qualitative similarity, but quantitative differences in mass–radius relationship of quark stars in these two models. Masses and radii are relatively larger and the central energy densities, required for stable quark stars, are lower in RHO model than that of bag model.

In this paper, we study perfect, anisotropic and anisotropic dissipative cylindrical quark star for the tilted observer. To this end, the field equations and dynamical equations are formulated and assume MIT bag model to find a numerical solution of the field equations. The behavior of resulting model is investigated by plotting density, pressure, anisotropy and energy conditions. We check viability of the solutions through physical features related to stellar matter configuration. Finally, we discuss stability for all the cases of fluid distribution.

Following our recently proposed self-consistent mean field approximation approach, we have done some researches on the chiral phase transition of strong interaction matter within the framework of Nambu-Jona-Lasinio (NJL) model. The chiral susceptibility and equation of state (EOS) are computed in this work for both two-flavor and three-flavor quark matter for contrast. The Pauli–Villars scheme, which can preserve gauge invariance, is used in this paper. Moreover, whether the three-flavor quark matter is more stable than the two-flavor quark matter or not in quark stars is discussed in this work. In our model, when the bag constant are the same, the two-flavor quark matter has a higher pressure than the three-flavor quark matter, which is different from what Witten proposed in his pioneering work.

We discuss the statistical mechanics and thermodynamics of quark matter at zero temperature and finite chemical potential using a thermodynamically consistent framework of quasiparticle model for QGP without the need of any reformulation of statistical mechanics or thermodynamical consistency relation. Using that equation of state, we solve the Tolman–Oppenheimer–Volkoff equation to obtain the mass-radius relation of dense quark star.

This work shows results for the EXO 0748-676 neutron star structure obtained with the use of a phenomenological quark matter description by taking into account a quark interaction, and observing the asymptotic freedom and the confinement characteristics of the fundamental theory. An appropriated choice of model parameters permit to reach the stability of compact dense stellar objects compatible with the observational data to the neutron star EXO 0748-676. It is assumed a color-flavor locked (CFL) superconducting phase to the ground state of the quark–gluon plasma formed in the object interior. We also discuss the surface properties of these objects, introducing a crust composed by a lattice of neutron-rich nucleus close to the neutron drip line, imbedded in an electron gas.

We investigate strongly interacting dense matter and neutron stars using a flavor-SU(3) approach based on a nonlinear realization of chiral symmetry. We study chiral symmetry restoration and the equation of state of stellar matter and determine neutron star properties using different sets of degrees of freedom. Finally, we include quarks in the model approach. We show the resulting phase diagram as well as hybrid star solutions for this model.

We analyze the magnetic field evolution in dense quark matter with unbroken chiral symmetry, which can be found inside quark and hybrid stars. The magnetic field evolves owing to the chiral magnetic effect in the presence of the electroweak interaction between quarks. In our study, we also take into account the magnetohydrodynamic turbulence effects in dense quark matter. We derive the kinetic equations for the spectra of the magnetic helicity density and the magnetic energy density as well as for the chiral imbalances. On the basis of the numerical solution of these equations, we find that turbulence effects are important for the behavior of small scale magnetic fields. It is revealed that, under certain initial conditions, these magnetic fields behave similarly to the electromagnetic flashes of some magnetars. We suggest that fluctuations of magnetic fields, described in frames of our model, which are created in the central regions of a magnetized compact star, can initiate magnetar bursts.

In this paper, we generate an anisotropic solution for a static sphere filled with quark matter in the framework of self-interacting Brans-Dicke theory. For this purpose, we add an anisotropic source in the seed distribution and decouple the field equations through deformation in the radial metric function. As a result of this transformation, the field equations are disintegrated into two systems which separately include the effects of isotropic and anisotropic sources. The system related to the additional source is solved via the MIT bag model equation of state. We consider Tolman V spacetime to formulate a solution for the isotropic sector which is extended to the anisotropic domain via decoupling technique. The junction conditions at the boundary determine the unknown parameters in terms of mass and radius of the spherical object. We investigate the viability and stability of the constructed strange star model in the presence of massive scalar field corresponding to the strange star candidate PSR J1614-2230. It is concluded that the anisotropic extension is well-behaved as it fulfills the necessary requirements of a physically acceptable model.

We perform hydrodynamical collapse and bounce simulations of neutron stars induced by QCD phase transition. We study how the phase transition affects the elements of the envelopes and crusts of neutron stars near the epoch of core-bounce. We assume the first-order phase transition, a chirally symmetric quark-gluon plasma for quark phase. The initial elements are adopted from the realistic evolutional calculations of neutron stars containing the cooling effects and the nucleosynthesis of envelope such as type I X-ray burst. We find that the elements of envelope can eject directly (without nucleosynthesis) for such a collapse and bounce by the transition.

The static spherically symmetric quark star structure is calculated by using an equation of state which takes into account the superconducting Color-Flavor Locked (CFL) phase of the strange quark matter. Some fundamental aspects of QCD (asymptotic freedom and confinement) are considered by using the phenomenological density-dependent quark mass model. We discuss the influence of model parameters on the conventional mass-radius relationship of a quark star structure. Massive quark stars are found due to the stiffness of the equation of state at low densities.