A generalized anisotropic model for super dense stars

A static anisotropic relativistic fluid sphere model with regular geometry and finite hydrostatic functions is presented. In the interior of the sphere, the density, radial pressure and tangential pressure are positives, monotonically decreasing with increasing radius and the radial pressure vanishes at the surface of the matter distribution and is joined continuously to the exterior Schwarzschild’s solution at this surface. The speeds of the radial and tangential sound are positive and lower than the speed of light, that is, the causal condition is not violated, and also the behavior of these guarantees that the model is potentially stable. Furthermore, the range of the compactness ratio is characteristic of compact stars and it is shown that the effect of the anisotropy generates that the speed of the radial sound can behave as a function monotonically increasing or monotonically decreasing.

A regular perfect fluid model for dense stars

We present an exact regular solution of Einstein equations for a static and spherically symmetric spacetime with a matter distribution of isotropic perfect fluid. The construction of the solution is realized assigning a regular potential [Formula: see text] and integrating the isotropic perfect fluid condition for the pressure. The resulting solution is physically acceptable, i.e. the geometry is regular and the hydrostatic variable pressure and density are positive regular monotonic decreasing functions, the speed of the sound is positive and smaller than the speed of the light. An important element of this solution is that its compactness value [Formula: see text] is in the characteristic range of compact stars, which makes a remarkable difference with other models with isotropic perfect fluid, this is [Formula: see text] so that we could represent compact stellar objects as neutron stars. In particular, for the maximum compactness of a star with a mass of [Formula: see text] the radius is [Formula: see text] and their central density [Formula: see text] is characteristic of compact stars.

A MEAN FIELD THEORY FOR THE COLD QUARK GLUON PLASMA APPLIED TO STELLAR STRUCTURE

The quark gluon plasma (QGP) at zero temperature and high baryon number is a strongly interacting system that may exist in the core of dense stars. Using an equation of state based on a mean-field approximation of QCD to describe this cold QGP, we study the structure of compact stars and obtain masses which are compatible with recent astrophysical data.

INTERACTION EFFECTS IN THE EQUATION OF STATE OF BARYONIC AND QUARK MATTER FOR DENSE STARS

Some specific aspects of the equation of state of strongly interacting baryonic and quark matter are addressed by substituting (at least in part) the usual numerical self-consistency of the mean field equations, eventually with corrections, by an analytical treatment of the dynamic equations of the components of such system. Several solutions can be found yielding different behaviors. The mean field solutions are partially extended.