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 EXTREMAL BLACK HOLES AND ELEMENTARY STRING STATES

1995 ◽  
Vol 10 (28) ◽  
pp. 2081-2093 ◽  
Author(s):  
ASHOKE SEN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Entropy ◽  
Extremal Black Hole ◽  
Coupling Constant ◽  
Left Handed ◽  
Quantum Numbers ◽  
Independent Parameters ◽  
Elementary String ◽  
Extremal Black Holes

Some of the extremal black hole solutions in string theory have the same quantum numbers as the Bogomol’nyi saturated elementary string states. We explore the possibility that these black holes can be identified with elementary string excitations. It is shown that stringy effects could correct the Bekenstein-Hawking formula for the black hole entropy in such a way that it correctly reproduces the logarithm of the density of elementary string states. In particular, this entropy has the correct dependence on three independent parameters, the mass and the left-handed charge of the black hole, and the string coupling constant.

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 Hairy black hole entropy and the role of solitons in three dimensions

2012 ◽  
Vol 2012 (2) ◽  
Author(s):  
Francisco Correa ◽  
Cristián Martínez ◽  
Ricardo Troncoso
Keyword(s):  
Black Hole ◽  
Black Hole Entropy ◽  
Three Dimensions ◽  
Hairy Black Hole

scholarly journals HOLOGRAPHY, GAUGE-GRAVITY CONNECTION AND BLACK HOLE ENTROPY

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3414-3425 ◽  
Author(s):  
PARTHASARATHI MAJUMDAR
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Degrees Of Freedom ◽  
Black Hole Entropy ◽  
Cross Sectional ◽  
Gauge Gravity ◽  
Thermal Stability Of ◽  
Spacetime Fluctuations ◽  
Area Law ◽  
Quantum Spacetime

The issues of holography and possible links with gauge theories in spacetime physics is discussed, in an approach quite distinct from the more restricted AdS-CFT correspondence. A particular notion of holography in the context of black hole thermodynamics is derived (rather than conjectured) from rather elementary considerations, which also leads to a criterion of thermal stability of radiant black holes, without resorting to specific classical metrics. For black holes that obey this criterion, the canonical entropy is expressed in terms of the microcanonical entropy of an Isolated Horizon which is essentially a local generalization of the very global event horizon and is a null inner boundary of spacetime, with marginal outer trapping. It is argued why degrees of freedom on this horizon must be described by a topological gauge theory. Quantizing this boundary theory leads to the microcanonical entropy of the horizon expressed in terms of an infinite series asymptotic in the cross-sectional area, with the leading 'area-law' term followed by finite, unambiguously calculable corrections arising from quantum spacetime fluctuations.

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 Ramanujan's influence on string theory, black holes and moonshine

2019 ◽  
Vol 378 (2163) ◽  
pp. 20180440 ◽  
Author(s):  
Jeffrey A. Harvey
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
String Theory ◽  
Modular Forms ◽  
Black Hole Entropy ◽  
Additional Material ◽  
Mock Modular Forms

Ramanujan influenced many areas of mathematics, but his work on q -series, on the growth of coefficients of modular forms and on mock modular forms stands out for its depth and breadth of applications. I will give a brief overview of how this part of Ramanujan's work has influenced physics with an emphasis on applications to string theory, counting of black hole states and moonshine. This paper contains the material from my presentation at the meeting celebrating the centenary of Ramanujan's election as FRS and adds some additional material on black hole entropy and the AdS/CFT correspondence. This article is part of a discussion meeting issue ‘Srinivasa Ramanujan: in celebration of the centenary of his election as FRS’.

Leading order of quantum corrections to black hole entropy sum relations

2019 ◽  
Vol 34 (32) ◽  
pp. 1950216
Author(s):  
Tairan Liang ◽  
Wei Xu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Physics ◽  
Black Hole Entropy ◽  
Flat Space ◽  
Quantum Corrections ◽  
Leading Order ◽  
Physics Of Black Holes ◽  
Mass Dependent ◽  
Modified Entropy

It has been found recently that the entropy relations of horizons have the universality of black hole mass-independence for many black holes. These universal entropy relations have some geometric and CFT understanding, which may provide further insight into the quantum physics of black holes. In this paper, we present the leading order of black hole entropy sum relations under the quantum corrections. It is found that the modified entropy sum becomes mass-dependent for some black holes in asymptotical (A)dS and flat space–times. We also give an example that the modified entropy sum of regular Bardeen AdS black holes is mass-independent, which may be quantized in the form of the electric charge and the cosmological constant.

BLACK HOLE ENTROPY IN STRING THEORY: GOING BEYOND BEKENSTEIN AND HAWKING

2006 ◽  
Vol 15 (10) ◽  
pp. 1561-1572 ◽  
Author(s):  
ATISH DABHOLKAR
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
String Theory ◽  
Recent Progress ◽  
Black Hole Entropy ◽  
Quantum Corrections ◽  
Corrected Entropy

In this talk I summarize some recent progress in string theory in understanding the entropy of a class of black holes including corrections to the Bekenstein–Hawking formula. The quantum corrected entropy is in precise numerical agreement with the logarithm of the number of microstates once quantum corrections are correctly taken into account.

scholarly journals A note on entropy relations of black hole horizons

2014 ◽  
Vol 29 (18) ◽  
pp. 1450088 ◽  
Author(s):  
Xin-He Meng ◽  
Wei Xu ◽  
Jia Wang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Black Hole Entropy ◽  
Higher Dimensions ◽  
Microscopic Level ◽  
Entropy Product ◽  
Product Part

Black holes with multi-horizons may provide new ways to understand the intrinsic thermodynamics. In this work, we focus on the entropy relations of black holes in three, four and higher dimensions. These entropy relations include entropy product, "part" entropy product and entropy sum. We also discuss their differences and similarities, in order to make a further study on understanding the origin of black hole entropy at the microscopic level.

scholarly journals TOWARDS A THEORY OF QUANTUM BLACK HOLES

2002 ◽  
Vol 17 (06n07) ◽  
pp. 979-988 ◽  
Author(s):  
VICTOR BEREZIN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mass Spectrum ◽  
Gravitational Collapse ◽  
Black Hole Entropy ◽  
Black Hole Mass ◽  
Quantum Black Hole ◽  
Classical Analog ◽  
Hole Model ◽  
Specific Quantum

We describe some specific quantum black hole model. It is pointed out that the origin of a black hole entropy is the very process of quantum gravitational collapse. The quantum black hole mass spectrum is extracted from the mass spectrum of the gravitating source. The classical analog of quantum black hole is constructed.

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