Radiating gravitational collapse with shear viscosity revisited

Abstract

A new model is proposed to a collapsing radiating star consisting of an isotropic fluid with shear viscosity undergoing radial heat flow with outgoing radiation. In a previous paper we have introduced a function time dependent into the g rr , besides the time dependent metric functions g θθ and g φφ . The aim of this work is to generalize this previous model by introducing shear viscosity and compare it to the non-viscous collapse. The behavior of the density, pressure, mass, luminosity and the effective adiabatic index is analyzed. Our work is compared to the case of a collapsing shearing fluid of a previous model, for a star with 6 M . The pressure of the star, at the beginning of the collapse, is isotropic but due to the presence of the shear the pressure becomes more and more anisotropic. The black hole is never formed because the apparent horizon formation condition is never satisfied. An observer at infinity sees a radial point source radiating exponentially until reaches the time of maximum luminosity and suddenly the star turns off. The effective adiabatic index has a very unusual behavior because we have a non-adiabatic regime in the fluid due to the heat flow.

The fallacy of Oppenheimer Snyder collapse: no general relativistic collapse at all, no black hole, no physical singularity

“…A generic study has shown that a contracting body on its way to continued collapse must tend to be radiation pressure dominated (Mitra 2006c). Several studies have also suggested that the contracting body may even radiate out its entire mass energy to avoid formation of trapped surfaces or horizons (Chan 2003;Fayos and Torres 2008;Pinheiro and Chan 2008).…”

The effect of a two-fluid atmosphere on relativistic stars

“…Moreover, (14) also suggests that given a form for the density, we can determine both the magnitude and the sign of the pressure. The sign of the pressure is crucial as it reveals more about the nature of the null fluid and the interaction of the fluid with the gravitational field.…”

“…The influence of pressure anisotropy, shear and bulk viscosity on the density, mass, luminosity and effective adiabatic index of an 8M contracting radiating star was studied by Chan [12,13]. These results were later extended by Pinheiro and Chan [14]. Misthry et al [15] generated nonlinear exact models in the shear-free regime for relativistic stars with heat flow, using a group theoretic approach that involves the Lie symmetry analysis of the Santos junction condition.…”

Kruskal Coordinates and Mass of Schwarzschild Black Holes: No Finite Mass Black Hole at All

“…In the absence of a trapped surface or EH, such objects must keep on radiating and contracting even if at infinitesimally slow rate. In fact there are several GTR special solutions for physical gravitational collapse which suggest that effect of radiation pressure and dissipation may cause formation of hot radiating ultra-compact objects rather that any BH or naked singularity [34,35]. Radiation pressure apart, generation of tangential pressure too can arrest the continued collapse.…”