Related papers: Hoop conjecture for colliding black holes : non-ti…
It has been well known that in the point of view of a distant observer, all in-falling matter to a black hole (BH) will be eventually stalled and "frozen" just outside the event horizon of the BH, although an in-falling observer will see…
The first objective of this work is to obtain practical prescriptions to calculate the absorption of mass and angular momentum by a black hole when external processes produce gravitational radiation. These prescriptions are formulated in…
Two seemingly distinct notions regarding black holes have captured the imagination of theoretical physicists over the past decade: First, black holes are conjectured to be fast scramblers of information, a notion that is further supported…
Primordial black holes (PBHs) are an attractive dark matter candidate, particularly if they can explain the totality of it. At PBH masses below $\sim 10^{17}$g and above $\sim 10^{23}$g this possibility is excluded from the variety of…
Black holes are often characterized by event horizons, following the literature that laid the mathematical foundations of the subject in the 1970s. However black hole event horizons have two fundamental conceptual limitations. First, they…
I discuss fundamental limits placed on information and information processing by gravity. Such limits arise because both information and its processing require energy, while gravitational collapse (formation of a horizon or black hole)…
We study curvature invariants in a binary black hole merger. It has been conjectured that one could define a quasi-local and foliation independent black hole horizon by finding the level--$0$ set of a suitable curvature invariant of the…
In calculations of gravitational collapse to form black holes, trapping horizons (foliated by marginally trapped surfaces) make their first appearance either within the collapsing matter or where it joins on to a vacuum exterior. Those…
Solar-mass black holes with masses in the range of $\sim 1-2.5 M_{\odot}$ are not expected from conventional stellar evolution, but can be produced naturally via neutron star (NS) implosions induced by capture of small primordial black…
The Event Horizon Telescope, a global submillimeter wavelength very long baseline interferometry array, produced the first image of supermassive black hole M87* showing a ring of diameter $\theta_d= 42\pm 3\,\mu$as, inferred a black hole…
The recent observation of gravitational waves confirms one of the most interesting predictions in general relativity: the black holes. Because the gravitational waves detected by LIGO fit very well within general relativity as a phenomenon…
When two objects have gravitational interaction between them, they are no longer independent of each other. In fact, there exists gravitational correlation between these two objects. Inspired by E. Verlinde's paper, we first calculate the…
We determine the causal structure of the McVittie spacetime for a cosmological model with an asymmetric bounce. The analysis includes the computation of trapping horizons, regular, trapped, and anti-trapped regions, and the integration of…
We critically examine the claim made by Burko and Ori that black holes are expected to form in nonsymmetric gravity and find their analysis to be inconclusive. Their conclusion is a result of the approximations they make, and not a…
Everybody knows what the classical black holes are. In short, this is a spacetime region beyond the so-called event horizon. The notion of the event horizon is mathematically well defined. The situation with a definition of quantum black…
It is thought that the final product of the gravitational collapse is a Kerr black hole and astronomers have discovered several good astrophysical candidates. While there is some indirect evidence suggesting that the latter have an event…
We set to weigh the black holes at their event horizons in various spacetimes and obtain masses which are substantially higher than their asymptotic values. In each case, the horizon mass of a Schwarzschild, Reissner-Nordstr{\"o}m, or Kerr…
Recent results of Trudinger on Isoperimetric Inequalities for non-convex bodies are applied to the gravitational collapse of a lightlike shell of matter to form a black hole. Using some integral identities for co-dimension two surfaces in…
The first LIGO-Virgo detections have confirmed the existence of massive black holes (BHs), with mass $30-40$ M$_\odot$. Such BHs might originate from massive metal-poor stars ($Z<0.3$ Z$_\odot$) or from gravitational instabilities in the…
We discuss the initial value problem of general relativity in its recently unified Lagrangian and Hamiltonian pictures and present a multi-domain pseudo-spectral collocation method to solve the resulting coupled nonlinear partial…