scholarly journals An entropy current and the second law in higher derivative theories of gravity

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Sayantani Bhattacharyya ◽  
Prateksh Dhivakar ◽  
Anirban Dinda ◽  
Nilay Kundu ◽  
Milan Patra ◽  
...  
Keyword(s):  
Black Hole ◽  
Equilibrium Configuration ◽  
Second Law Of Thermodynamics ◽  
Alternative Proof ◽  
Second Law ◽  
Higher Derivative ◽  
Entropy Current ◽  
Theories Of Gravity ◽  
Dynamical Fluctuations ◽  
Set Up

Abstract We construct a proof of the second law of thermodynamics in an arbitrary diffeomorphism invariant theory of gravity working within the approximation of linearized dynamical fluctuations around stationary black holes. We achieve this by establishing the existence of an entropy current defined on the horizon of the dynamically perturbed black hole in such theories. By construction, this entropy current has non-negative divergence, suggestive of a mechanism for the dynamical black hole to approach a final equilibrium configuration via entropy production as well as the spatial flow of it on the null horizon. This enables us to argue for the second law in its strongest possible form, which has a manifest locality at each space-time point. We explicitly check that the form of the entropy current that we construct in this paper exactly matches with previously reported expressions computed considering specific four derivative theories of higher curvature gravity. Using the same set up we also provide an alternative proof of the physical process version of the first law applicable to arbitrary higher derivative theories of gravity.

scholarly journals Black Hole Entropy for Two Higher Derivative Theories of Gravity

Entropy ◽  
2010 ◽  
Vol 12 (10) ◽  
pp. 2186-2198 ◽  
Author(s):  
Emilio Bellini ◽  
Roberto Di Criscienzo ◽  
Lorenzo Sebastiani ◽  
Sergio Zerbini
Keyword(s):  
Black Hole ◽  
Black Hole Entropy ◽  
Higher Derivative ◽  
Theories Of Gravity

Thermodynamics, Quantum Physics, and Black Holes

2020 ◽  
pp. 24-39
Author(s):  
John W. Moffat
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Mechanics ◽  
Quantum Physics ◽  
Second Law Of Thermodynamics ◽  
Information Loss ◽  
Second Law ◽  
Major Question ◽  
Long Time ◽  
Information Loss Problem

A major question confronting physicists studying black holes was whether thermodynamics applied to them—that is, whether the black holes radiated heat and lost energy. Bekenstein considered heat and thermodynamics important for the interior of black holes. Based on the second law of thermodynamics, Hawking proposed that black holes evaporate over a very long time through what we now call Hawking radiation. This concept contradicts the notion that nothing can escape a black hole event horizon. Quantum physics enters into Hawking’s calculations, and he discovered the conundrum that the radiation would violate quantum mechanics, leading to what is called the information loss problem. These ideas are still controversial, and many physicists have attempted to resolve them, including Russian theorists Zel’dovich and Starobinsky. Alternative quantum physics interpretations of black holes have been proposed that address the thermodynamics problems, including so-called gravastars.

scholarly journals Hawking radiation from universal horizons

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Mario Herrero-Valea ◽  
Stefano Liberati ◽  
Raquel Santos-Garcia
Keyword(s):  
Black Hole ◽  
Hawking Radiation ◽  
Black Hole Thermodynamics ◽  
Second Law ◽  
Consistency Test ◽  
First Law Of Thermodynamics ◽  
Generalized Second Law ◽  
Theories Of Gravity ◽  
Per Se ◽  
Suitable Notion

Abstract The persistence of a suitable notion of black hole thermodynamics in Lorentz breaking theories of gravity is not only a non-trivial consistency test for such theories, it is also an interesting investigation per se, as it might help us identifying the crucial features at the root of these surprising laws governing such purely gravitational objects. In past investigations, controversial findings were presented in this sense. With the aim of settling this issue, we present here two complementary derivations of Hawking radiation in geometries endowed with universal horizons: a novel feature of back holes in Lorentz breaking theories of gravity which reproduces several properties normally characterizing Killing horizons. We find that both the derivations agree on the fact that the Hawking temperature associated to these geometries is set by the generalized universal horizon peeling surface gravity, as required for consistency with extant derivations of the first law of thermodynamics for these black holes. We shall also comment on the compatibility of our results with previous alternative derivations and on their significance for the survival of the generalized second law of black hole thermodynamics in Lorentz breaking theories of gravity.

THOUGHTS ON THE AREA THEOREM

2009 ◽  
Vol 24 (16n17) ◽  
pp. 3111-3135 ◽  
Author(s):  
MU-IN PARK
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Three Dimensional ◽  
Kerr Black Hole ◽  
Second Law Of Thermodynamics ◽  
Positive Energy ◽  
Btz Black Hole ◽  
Area Theorem ◽  
Four Dimensions ◽  
Higher Derivative

Hawking's area theorem can be understood from a quasistationary process in which a black hole accretes positive energy matter, independent of the details of the gravity action. I use this process to study the dynamics of the inner as well as the outer horizons for various black holes which include the recently discovered exotic black holes and three-dimensional black holes in higher derivative gravities as well as the usual Banados–Teitelboim–Zanelli (BTZ) black hole and the Kerr black hole in four dimensions. I find that the area for the inner horizon "can decrease," rather than increase, with the quasistationary process. However, I find that the area for the outer horizon "never decrease" such as the usual area theorem still works in our examples, though this is quite nontrivial in general. I also find that the recently proposed new entropy formulae for the above mentioned, recently discovered black holes satisfy the second law of thermodynamics.

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