We propose that the gravitational collapse of supermassive stars (M ∼> 5× 10 M⊙) could be a cosmological source of γ-ray bursts. Supermassive stars could form as an intermediate step in the collapse of relativistic star clusters, or in supermassive clouds with inefficient cooling. Supermassive stars would be de-stabilized by the Feynman-Chandrasekhar instability and could collapse to black hole...

We present an investigation of massive star formation that results from the gravitational collapse of massive, magnetized molecular cloud cores. We investigate this by means of highly resolved, numerical simulations of initial magnetized Bonnor-Ebert-Spheres that undergo collapse and cooling. By comparing three different cases an isothermal collapse, a collapse with radiative cooling, and a mag...

Critical gravitational collapse and self similarity are used to probe the mass distribution of subsolar objects. We demonstrate that at very low mass the distribution is given by a power law, with an exponent opposite in sign to that observed at high-mass regime. We further show that the value of this low-mass exponent is in principle calculable via dynamical systems theory applied to gravitati...

First results of a numerical investigation of primordial black hole formation in the radiation dominated phase of the Early Universe are presented. The simulations follow the gravitational collapse of three different families of high-amplitude density fluctuations imposed at the time of horizon crossing. The threshold for black hole formation, δc ≈ 0.7, is found to be nearly identical for all p...

We perform 3+1 general relativistic simulations of rotating core collapse in the context of the collapsar model for long gamma-ray bursts. We employ a realistic progenitor, rotation based on results of stellar evolution calculations, and a simplified equation of state. Our simulations track self-consistently collapse, bounce, the postbounce phase, black hole formation, and the subsequent early ...

We analyze the mode-coupling phenomena in realistic rotating gravitational collapse. Physically, this phenomena is caused by the dragging of reference frames, due to the black-hole (or star’s) rotation. It is shown that different modes become coupled during the rotating collapse. As a consequence, the asymptotic late-time tails are dominated by modes which, in general, have an angular distribut...

I discuss the statistical mechanics of gravitating systems and in particular its cosmological implications, and argue that many conventional views on this subject in the foundations of statistical mechanics embody significant confusion; I attempt to provide a clearer and more accurate account. In particular, I observe that (i) the role of gravity in entropy calculations must be distinguished fr...

Critical behavior in gravitational collapse, as first found by Choptuik @1#, occurs at and near the threshold of black hole formation @2#. For a one-parameter family of initial data slightly above the threshold, the mass of the black hole, M BH , scales like (p2p*) . Here p is the parameter, p* is its critical value and g is a constant that depends on the type of matter, but not on the family o...