Related papers: Workshop on the limiting compactness objects: Blac…
The Schwarzschild metric has a divergent energy density at the horizon, which motivates a new approach to black holes. If matter is spread uniformly throughout the interior of a supermassive black hole, with mass $M\sim M_\star= 2.34…
We investigate the shadow of an exact black hole solution of Einstein's equations recently proposed by Cardoso et al., to describe a supermassive black hole immersed in a dark matter halo. We analyze and discuss the light rings and the…
It was shown long back in \cite{Dadhich97} that a non-extremal black hole cannot be converted into an extremal one by test particle adiabatic accretion. The Buchdahl star is the most compact object without horizon and is defined by $\Phi(R)…
We consider the steady-state density and velocity dispersion profiles of collisionless matter around a Schwarzschild black hole (BH) and its associated rate of accretion onto the BH. We treat matter, which could be stars or dark matter…
Various observations from cosmic microwave background radiation (CMBR), type Ia supernova and baryon acoustic oscillations (BAO) are strongly suggestive of an accelerated expansion of the universe which can be explained by the presence of…
This article was co-authored by all invited speakers at the Joint Discussion on `Neutron Stars and Black Holes in Star Clusters,' which took place during the IAU General Assembly in Prague, Czech Republic, on August 17 and 18, 2006. Each…
We have recently proposed a model for a regular black hole, or an ultra-compact object, that is premised on having maximally negative radial pressure throughout the entirety of the object's interior. This model can be viewed as that of a…
In this work we show that single horizon black hole behaves as a "laser". It is in many aspects conceptually analogous to Corley and Jacobson work on the two horizon black hole "laser". We started by proposition that circumference of the…
There is accumulating evidence that (fundamental) scalar fields may exist in Nature. The gravitational collapse of such a boson cloud would lead to a boson star (BS) as a new type of a compact object. Similarly as for white dwarfs and…
We describe a unitary scattering process, as observed from spatial infinity, of massless scalar particles on an asymptotically flat Schwarzschild black hole background. In order to do so, we split the problem in two different regimes…
Buchdahl sphere, the limiting stable isotropic stellar structure without exotic matter, plays a very important role in our understanding of how compact an astrophysical object can be. Here, we show certain universal properties associated…
This article is based on a pair of lectures given at the 2005 SLAC Summer Institute. Our goal is to motivate why most physicists and astrophysicists accept the hypothesis that the most massive, compact objects seen in many astrophysical…
The stability and other physical properties of a class of regular black holes, quasiblack holes, and other electrically charged compact objects are investigated in the present work. The compact objects are obtained by solving the…
We investigate the stability of ultra-compact stellar configurations in the context of an interacting vacuum component. By extending the Tolman-Oppenheimer-Volkoff equations to include a covariant energy exchange between the fluid and…
We propose a no horizon black hole whose collapsing matter condenses close to the event horizon and before its formation. Compared to Vaz's model [arXiv: 1407.3823], our interior geometry depends only on one parameter $r_{0}$ - the radius…
We propose a novel solution for the endpoint of gravitational collapse, in which spacetime ends (and is orbifolded) at a microscopic distance from black hole event horizons. This model is motivated by the emergence of singular event…
This paper investigates Buchdahl transformations within the framework of Einstein and Einstein-Scalar theories. Specifically, we establish that the recently proposed Schwarzschild-Levi-Civita spacetime can be obtained by means of a Buchdahl…
In the context of General Relativity, black holes are not allowed to possess scalar hair, wormholes are not traversable and particle-like solutions are irregular. Therefore, in order to derive novel and physically interesting solutions that…
Black hole entropy appears to be ``universal''--many independent calculations, involving models with very different microscopic degrees of freedom, all yield the same density of states. I discuss the proposal that this universality comes…
The existence of both a minimum mass and a minimum density in nature, in the presence of a positive cosmological constant, is one of the most intriguing results in classical general relativity. These results follow rigorously from the…