相关论文: Maximum bounds on the surface redshift of anisotro…
We study the effects of anisotropic pressure on the properties of spherically symmetric, gravitationally bound objects. We consider the full general relativistic treatment of this problem and obtain exact solutions for various form of…
We derive upper and lower limits for the basic physical parameters (mass-radius ratio, anisotropy, redshift and total energy) for arbitrary anisotropic general relativistic matter distributions in the presence of a cosmological constant.…
At finite temperature (T) there is a link with general relativity and hydrodynamics that leads to a lower bound for the ratio of shear viscosity and entropy density (\eta/s). We find that the bound is saturated in the simple model for quark…
An analysis of radiating perfect fluid models with asymptotically AdS boundary conditions is presented. Such scenarios consist of a spherical gas of radiation (a "star") localised near the centre of the spacetime due to the confining nature…
An anisotropic fluid with variable energy density and negative pressure is proposed, both outside and inside stars. The gravitational field is constant everywhere in free space (if we neglect the local contributions) and its value is of the…
We study the physical features of a class of exact solutions for cold compact anisotropic stars. The effect of pressure anisotropy on the maximum mass and surface redshift is analysed in the Vaidya-Tikekar model. It is shown that maximum…
An infinite class of exact static anisotropic spheres is developed. All members of the class satisfy (i) regularity (meaning no singularities), and in particular at the origin, (ii) positive but monotone decreasing energy density…
We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for anisotropic neutral fluid, compatible with a super dense star modeling by considering a specific choice of anisotropy…
I report on recent work concerning the existence and stability of self-gravitating spheres with anisotropic pressure. After presenting new exact solutions, Chandrasekhar's variational formalism for radial perturbations is generalized to…
The peak star formation intensity in starburst galaxies does not vary significantly from the local universe to redshift z~6. We arrive at this conclusion through new surface brightness measurements of 47 starburst galaxies at z~5-6,…
It is well known that a spherically symmetric constant density static star, modeled as a perfect fluid, possesses a bound on its mass m by its radial size R given by 2m/R \le 8/9 and that this bound continues to hold when the energy density…
The anisotropy of pressure arises due to the various complex phenomena that happen inside the neutron star (NS). In this study, we calculate the degree of anisotropy inside the NS using the scalar pressure anisotropy model. Macroscopic…
Observations in the rest frame ultraviolet from various space missions are used to define the nearby starburst regions having the highest surface brightness on scales of several hundred pc. The bright limit is found to be 6x10^-16…
We study nonaxisymmetric perturbations of rotating relativistic stars. modeled as perfect-fluid equilibria. Instability to a mode with angular dependence $\exp(im\phi)$ sets in when the frequency of the mode vanishes. The locations of these…
High energy density ($\eps$) and temperature (T) links general relativity and hydrodynamics leading to a lower bound for the ratio of shear viscosity ($\eta$) and entropy density ($s$). We get the interesting result that the bound is…
For general relativistic equilibrium stellar models (stationary axisymmetric asymptotically flat and convection-free) with differential rotation, it is shown that for a wide class of rotation laws the distribution of angular velocity of the…
The ratio of total mass $M$ to surface radius $R$ of spherical perfect fluid ball has an upper bound, $M/R < B$. Buchdahl obtained $B = 4/9$ under the assumptions; non-increasing mass density in outward direction, and barotropic equation of…
An estimate of the maximum observable redshift is obtained using only t_{0} approximately equal to (14+- 3)10^{9}years, H_{0} approximately equal to 65 +- 10Km\sec^{-1}Mpc^{-1}(t_{0}H_{0} approximately equal to 0.91 +- 0.08/0.18) assuming…
When the surface angular velocity is above about 70% of the critical angular velocity, many interesting features appear which may be tested by interferometric observations, like significant deformation of stars, variation of the effective…
We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for charged fluid with pressure anisotropy, compatible with a super dense star modeling. Further, we have constructed an…