scholarly journals Symmetries of the black hole interior and singularity regularization

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Marc Geiller ◽  
Etera R. Livine ◽  
Francesco Sartini
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Physics ◽  
Proper Time ◽  
White Hole ◽  
Formula Group ◽  
Physical Symmetry ◽  
Black Hole Interior ◽  
Group Quantization

We reveal an \mathfrak{iso}(2,1)𝔦𝔰𝔬(2,1) Poincar'e algebra of conserved charges associated with the dynamics of the interior of black holes. The action of these Noether charges integrates to a symmetry of the gravitational system under the Poincar'e group ISO(2,1)(2,1), which allows to describe the evolution of the geometry inside the black hole in terms of geodesics and horocycles of AdS{}_22. At the Lagrangian level, this symmetry corresponds to M"obius transformations of the proper time together with translations. Remarkably, this is a physical symmetry changing the state of the system, which also naturally forms a subgroup of the much larger \textrm{BMS}_{3}=\textrm{Diff}(S^1)\ltimes\textrm{Vect}(S^1)BMS3=Diff(S1)⋉Vect(S1) group, where S^1S1 is the compactified time axis. It is intriguing to discover this structure for the black hole interior, and this hints at a fundamental role of BMS symmetry for black hole physics. The existence of this symmetry provides a powerful criterion to discriminate between different regularization and quantization schemes. Following loop quantum cosmology, we identify a regularized set of variables and Hamiltonian for the black hole interior, which allows to resolve the singularity in a black-to-white hole transition while preserving the Poincar'e symmetry on phase space. This unravels new aspects of symmetry for black holes, and opens the way towards a rigorous group quantization of the interior.

scholarly journals Black hole and neutron star mergers in galactic nuclei: the role of triples

2019 ◽  
Vol 488 (2) ◽  
pp. 2825-2835 ◽  
Author(s):  
Giacomo Fragione ◽  
Nathan W C Leigh ◽  
Rosalba Perna
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Massive Stars ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Compact Objects ◽  
Large Numbers ◽  
Binary Case

ABSTRACT Nuclear star clusters that surround supermassive black holes (SMBHs) in galactic nuclei are thought to contain large numbers of black holes (BHs) and neutron stars (NSs), a fraction of which form binaries and could merge by Kozai–Lidov oscillations (KL). Triple compact objects are likely to be present, given what is known about the multiplicity of massive stars, whose life ends either as an NS or a BH. In this paper, we present a new possible scenario for merging BHs and NSs in galactic nuclei. We study the evolution of a triple black hole (BH) or neutron star (NS) system orbiting an SMBH in a galactic nucleus by means of direct high-precision N-body simulations, including post-Newtonian terms. We find that the four-body dynamical interactions can increase the KL angle window for mergers compared to the binary case and make BH and NS binaries merge on shorter time-scales. We show that the merger fraction can be up to ∼5–8 times higher for triples than for binaries. Therefore, even if the triple fraction is only ∼10–$20\rm{\,per\,cent}$ of the binary fraction, they could contribute to the merger events observed by LIGO/VIRGO in comparable numbers.

scholarly journals Ten shades of black

2015 ◽  
Vol 24 (12) ◽  
pp. 1544007 ◽  
Author(s):  
Shahar Hod
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Radiation Spectrum ◽  
Black Hole Physics ◽  
Black Body ◽  
Black Hole Radiation ◽  
Dimensional Spacetime ◽  
Opposite Behavior ◽  
Curvature Potential ◽  
Energy Dependent

The holographic principle has taught us that, as far as their entropy content is concerned, black holes in (3 + 1)-dimensional curved spacetimes behave as ordinary thermodynamic systems in flat (2 + 1)-dimensional spacetimes. In this paper, we point out that the opposite behavior can also be observed in black-hole physics. To show this we study the quantum Hawking evaporation of near-extremal Reissner–Nordström (RN) black holes. We first point out that the black-hole radiation spectrum departs from the familiar radiation spectrum of genuine (3 + 1)-dimensional perfect black-body emitters. In particular, the would be black-body thermal spectrum is distorted by the curvature potential which surrounds the black-hole and effectively blocks the emission of low-energy quanta. Taking into account the energy-dependent gray-body factors which quantify the imprint of passage of the emitted radiation quanta through the black-hole curvature potential, we reveal that the (3 + 1)-dimensional black holes effectively behave as perfect black-body emitters in a flat (9 + 1)-dimensional spacetime.

scholarly journals Matter Accretion Versus Semiclassical Bounce in Schwarzschild Interior

Universe ◽  
2020 ◽  
Vol 6 (10) ◽  
pp. 178
Author(s):  
Kirill Bronnikov ◽  
Sergey Bolokhov ◽  
Milena Skvortsova
Keyword(s):  
Black Hole ◽  
Vacuum Polarization ◽  
Particle Production ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Schwarzschild Black Hole ◽  
White Hole ◽  
Stress Energy ◽  
Black Hole Interior ◽  
Nontrivial Topology

We discuss the properties of the previously constructed model of a Schwarzschild black hole interior where the singularity is replaced by a regular bounce, ultimately leading to a white hole. We assume that the black hole is young enough so that the Hawking radiation may be neglected. The model is semiclassical in nature and uses as a source of gravity the effective stress-energy tensor (SET) corresponding to vacuum polarization of quantum fields, and the minimum spherical radius is a few orders of magnitude larger than the Planck length, so that the effects of quantum gravity should still be negligible. We estimate the other quantum contributions to the effective SET, caused by a nontrivial topology of spatial sections and particle production from vacuum due to a nonstationary gravitational field and show that these contributions are negligibly small as compared to the SET due to vacuum polarization. The same is shown for such classical phenomena as accretion of different kinds of matter to the black hole and its further motion to the would-be singularity. Thus, in a clear sense, our model of a semiclassical bounce instead of a Schwarzschild singularity is stable under both quantum and classical perturbations.

scholarly journals The Role of Gravitational Instabilities in the Feeding of Supermassive Black Holes

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Giuseppe Lodato
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
High Redshift ◽  
Supermassive Black Holes ◽  
Point Of View ◽  
Accretion Discs ◽  
Theoretical Point ◽  
Interstellar Gas ◽  
Massive Black Hole

I review the recent progresses that have been obtained, especially through the use of high-resolution numerical simulations, on the dynamics of self-gravitating accretion discs. A coherent picture is emerging, where the disc dynamics is controlled by a small number of parameters that determine whether the disc is stable or unstable, whether the instability saturates in a self-regulated state or runs away into fragmentation, and whether the dynamics is local or global. I then apply these concepts to the case of AGN discs, discussing the implications of such evolution on the feeding of supermassive black holes. Nonfragmenting, self-gravitating discs appear to play a fundamental role in the process of formation of massive black hole seeds at high redshift ( 10–15) through direct gas collapse. On the other hand, the different cooling properties of the interstellar gas at low redshifts determine a radically different behaviour for the outskirts of the accretion discs feeding typical AGNs. Here the situation is much less clear from a theoretical point of view, and while several observational clues point to the important role of massive discs at a distance of roughly a parsec from their central black hole, their dynamics is still under debate.

scholarly journals Dark Matter on the Closed Region Connected With Black Hole by Wormhole

2021 ◽  
Author(s):  
Mostafa Bousder
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Hopf Fibration ◽  
Closed Region ◽  
White Hole

In this letter, instead of choosing the Einstein Rosen bridge between two black holes as in ER=EPR, we consider a wormhole between a black hole and a closed edge of the wormhole. We assume that information in a black hole travels through a wormhole, turns to mass (dark matter) in the closed region. This study is in contradiction with the existence of the white hole in our Universe. We replace the notion of the white hole with the massive closed region. We prove the metric of the closed region by the Hopf fibration, this new metric generalizes the $AdS_{5}$\ metric.

scholarly journals Three puzzles in cosmology

2020 ◽  
Vol 29 (14) ◽  
pp. 2030013
Author(s):  
Samir D. Mathur
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Theory ◽  
Black Hole Physics ◽  
Information Paradox ◽  
Fundamental Structure

Cosmology presents us with several puzzles that are related to the fundamental structure of quantum theory. We discuss three such puzzles, linking them to effects that arise in black hole physics. We speculate that puzzles in cosmology may be resolved by the vecro structure of the vacuum that resolves the information paradox and the “bags of gold” problem for black holes.

scholarly journals Comment on “Black Hole Entropy: A Closer Look”

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1110
Author(s):  
Pedro Pessoa ◽  
Bruno Arderucio Costa
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Entropy ◽  
Additive Functional ◽  
Important Distinction

In a recent paper (Entropy 2020, 22(1), 17), Tsallis states that entropy—as in Shannon or Kullback–Leiber’s definitions—is inadequate to interpret black hole entropy and suggests that a new non-additive functional should take the role of entropy. Here we counterargue by explaining the important distinction between the properties of extensivity and additivity; the latter is fundamental for entropy, while the former is a property of particular thermodynamical systems that is not expected for black holes. We also point out other debatable statements in his analysis of black hole entropy.

scholarly journals Small Black/White Hole Stability and Dark Matter

Universe ◽  
2018 ◽  
Vol 4 (11) ◽  
pp. 127 ◽  
Author(s):  
Carlo Rovelli ◽  
Francesca Vidotto
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Loop Quantum Gravity ◽  
Quantum Superposition ◽  
White Hole ◽  
Small Black Hole ◽  
Black And White ◽  
Minimal Eigenvalue ◽  
Simple Quantum

We show that the expected lifetime of white holes formed as remnants of evaporated black holes is consistent with their production at reheating. We give a simple quantum description of these objects and argue that a quantum superposition of black and white holes with large interiors is stable, because it is protected by the existence of a minimal eigenvalue of the area, predicted by Loop Quantum Gravity. These two results support the hypothesis that a component of dark matter could be formed by small black hole remnants.

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