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Gravitational vacuum condensate stars, also known as gravastars, have been proposed as an alternative to black holes. Their interior contains a perfect fluid with an equation of state akin to that of a cosmological constant. For this…

General Relativity and Quantum Cosmology · Physics 2023-08-16 P. P. Avelino

We investigate the idea that ultrahigh energy gamma-rays (E>10 TeV) can be produced when charged particles are accelerated by microscopic black holes. We begin by showing that microscopic black holes may exist as remnants of primordial…

Astrophysics · Physics 2009-11-07 Roberto Casadio , Benjamin Harms , Octavian Micu

We use simulations of hydrodynamics coupled with full general relativity to investigate the gravitational waves produced by a star colliding with a massive black hole when the star's tidal disruption radius lies far outside of the black…

General Relativity and Quantum Cosmology · Physics 2014-10-24 William E. East

Quantum entanglement lies at the heart of quantum information theory, with applications to quantum computing, teleportation, cryptography and communication. In the apparently separate world of quantum gravity, the Hawking effect of…

High Energy Physics - Theory · Physics 2017-08-23 M. J. Duff

It was recently suggested that "cosmologically coupled" black holes with masses that increase in proportion to the volume of the Universe might constitute the physical basis of dark energy. We take this claim at face value and discuss its…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-25 Sohan Ghodla , Richard Easther , M. M. Briel , J. J. Eldridge

Gravitational field is usually neglected in calculation of atomic energy levels as its effect is much weaker than the electromagnetic field, but that is not the case for a particle orbiting a black hole. In this work, canonical quantization…

General Relativity and Quantum Cosmology · Physics 2023-09-12 David Senjaya

The Hawking-Penrose singularity theorem states that a singularity forms inside a black hole in general relativity. To remove this singularity one must resort to a more fundamental theory. Using a corrected dynamical equation arising in loop…

General Relativity and Quantum Cosmology · Physics 2018-01-15 Changjun Gao , Youjun Lu , You-Gen Shen , Valerio Faraoni

We consider how an advanced civilization might build a radiator to send gravitational waves signals by using small black holes. Micro black holes on the scale of centimeters but with masses of asteroids to planets are manipulated with a…

Popular Physics · Physics 2018-06-22 A. A. Jackson , Gregory Benford

Black holes are considered among the most fascinating objects that exist in our universe, since in the classical formalism nothing, even no light, can escape from their vicinity due to gravity. The gravitational potential causes the light…

Quantum Physics · Physics 2023-07-03 Sayan Jana , Lea Sirota

Studies have proposed that there is evidence for cosmological coupling of black holes (BHs) with an index of $k\approx 3$; hence, BHs serve as the astrophysical source of dark energy. However, the data sample is limited for the redshifts of…

One possible channel for black hole formation is the collapse of a rigidly rotating massive neutron star as it loses its angular momentum or gains excessive mass through accretion. It was proposed that part of the neutron star may form a…

High Energy Astrophysical Phenomena · Physics 2015-10-28 Ben Margalit , Brian D. Metzger , Andrei M. Beloborodov

Since the seminal work of Penrose (1969) and Blandford & Znajek (1977), it has been realized that black hole spin may be an important energy source in astrophysics. The radio-loud/radio-quiet dichotomy in the AGN population is usually…

High Energy Astrophysical Phenomena · Physics 2009-03-25 L. Brenneman , J. M. Miller , K. Nandra , M. Volonteri , M. Cappi , G. Matt , S. Kitamoto , F. Paerels , M. Mendez , R. Smith , M. Nowak , M. Garcia , M. Watson , M. Weisskopf , Y. Terashima , Y. Ueda

I reconsider Hawking's analysis of the effects of gravitational collapse on quantum fields, taking into account interactions between the fields. The ultra-high energy vacuum fluctuations, which had been considered to be an awkward…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Adam D. Helfer

We study the black hole particle production in a regular spacetime metric obtained in a minisuperspace approach to loop quantum gravity. In different previous papers the static solution was obtained and shown to be singularity-free and…

General Relativity and Quantum Cosmology · Physics 2011-02-01 Emanuele Alesci , Leonardo Modesto

Black hole complementarity is incompatible with the existence of traversable wormholes. In fact, traversable wormholes cause problems for any theory where information comes out in the Hawking radiation.

High Energy Physics - Theory · Physics 2009-10-28 Daniel Gottesman

Models with extra spatial dimensions and TeV-scale gravity offer the first opportunity to test the conjecture of black hole formation in trans-Planckian energy scattering with small impact parameters. After a brief review of gravitational…

High Energy Physics - Phenomenology · Physics 2009-11-07 Huitzu Tu

We review recent work on the Hawking radiation of rotating brane black holes, as may be produced at the LHC. We outline the methodology for calculating the fluxes of particles, energy and angular momentum by spin-0, spin-1/2 and spin-1…

High Energy Physics - Theory · Physics 2007-08-28 Elizabeth Winstanley

The existence of black holes and of spacetime singularities is a fundamental issue in science. Despite this, observations supporting their existence are scarce, and their interpretation unclear. We overview how strong a case for black holes…

General Relativity and Quantum Cosmology · Physics 2017-09-07 Vitor Cardoso , Paolo Pani

Limits on the dark matter fraction of small mass primordial black holes from Hawking radiation are predominantly derived from the assumption of a Schwarzschild black hole evaporating. However, astrophysical black holes are usually much more…

General Relativity and Quantum Cosmology · Physics 2026-04-03 Sebastian Schuster , Jessica Santiago , Justin Feng , Matt Visser

We investigate the energy distribution of a black hole in various spacetimes as reckoned by a distant observer using the quasi-local energy approach. In each case the horizon mass of a black hole: neutral, charged or rotating, is found to…

General Relativity and Quantum Cosmology · Physics 2019-02-27 Yuan K. Ha