scholarly journals General theory of large D membranes consistent with second law of thermodynamics

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Arunabha Saha
Keyword(s):  
Black Holes ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Local Form ◽  
Leading Order ◽  
Stationary Black Hole ◽  
Simple Modification ◽  
Entropy Current ◽  
Additional Constraints ◽  
Stationary Membrane

Abstract We write down the most general membrane equations dual to black holes for a general class of gravity theories, up to sub-leading order in 1/D in large D limit. We derive a “minimal” entropy current which satisfies a local form of second law from these membrane equations. We find that consistency with second law requires the membrane equations to satisfy certain constraints. We find additional constraints on the membrane equations from the existence of membrane solutions dual to stationary black holes. Finally we observe a tension between second law and matching with Wald entropy for dual stationary black hole configurations, for the minimal entropy current. We propose a simple modification of the membrane entropy current so that it satisfies second law and also the stationary membrane entropy matches the Wald entropy.

scholarly journals The maximum efficiency of nano heat engines depends on more than temperature

Quantum ◽  
2019 ◽  
Vol 3 ◽  
pp. 177 ◽  
Author(s):  
Mischa P. Woods ◽  
Nelly Huei Ying Ng ◽  
Stephanie Wehner
Keyword(s):  
Second Law Of Thermodynamics ◽  
Maximum Efficiency ◽  
Second Law ◽  
Single Shot ◽  
Free Energies ◽  
Heat Engines ◽  
A Value ◽  
Quantum Protocols ◽  
Additional Constraints ◽  
Quantum Heat Engines

Sadi Carnot's theorem regarding the maximum efficiency of heat engines is considered to be of fundamental importance in thermodynamics. This theorem famously states that the maximum efficiency depends only on the temperature of the heat baths used by the engine, but not on the specific structure of baths. Here, we show that when the heat baths are finite in size, and when the engine operates in the quantum nanoregime, a revision to this statement is required. We show that one may still achieve the Carnot efficiency, when certain conditions on the bath structure are satisfied; however if that is not the case, then the maximum achievable efficiency can reduce to a value which is strictly less than Carnot. We derive the maximum efficiency for the case when one of the baths is composed of qubits. Furthermore, we show that the maximum efficiency is determined by either the standard second law of thermodynamics, analogously to the macroscopic case, or by the non increase of the max relative entropy, which is a quantity previously associated with the single shot regime in many quantum protocols. This relative entropic quantity emerges as a consequence of additional constraints, called generalized free energies, that govern thermodynamical transitions in the nanoregime. Our findings imply that in order to maximize efficiency, further considerations in choosing bath Hamiltonians should be made, when explicitly constructing quantum heat engines in the future. This understanding of thermodynamics has implications for nanoscale engineering aiming to construct small thermal machines.

scholarly journals Phantom accretion by black holes and the generalized second law of thermodynamics

2010 ◽  
Vol 33 (5-6) ◽  
pp. 292-295 ◽  
Author(s):  
J.A.S. Lima ◽  
S.H. Pereira ◽  
J.E. Horvath ◽  
Daniel C. Guariento
Keyword(s):  
Black Holes ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Generalized Second Law

scholarly journals Extremal bifurcations of rotating AdS4 black holes

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Brett McInnes
Keyword(s):  
Black Holes ◽  
Magnetic Charge ◽  
Second Law Of Thermodynamics ◽  
Basic Question ◽  
Quantum Mechanical ◽  
Second Law ◽  
Rapid Rotation ◽  
Spinning Particles ◽  
Weak Gravity ◽  
Extremal Black Holes

Abstract The Weak Gravity Conjecture arises from the assertion that all extremal black holes, even those which are “classical” in the sense of being very massive, must decay by quantum-mechanical emission of particles or smaller black holes. This is interesting, because some observed astrophysical black holes are on the brink of being extremal — though this is due to rapid rotation rather than a large electric or magnetic charge. The possibility that rotating near-extremal black holes might, in addition to radiating spinning particles, also bifurcate by emitting smaller black holes, has attracted much attention of late. There is, however, a basic question to be answered here: can such a bifurcation be compatible with the second law of thermodynamics? This is by no means clear. Here we show that, if there is indeed such a mechanism for bifurcations of AdS4-Kerr-Newman black holes, then this process can in fact satisfy the second law.

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 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.

GRAVITATION AND THE SECOND LAW OF THERMODYNAMICS

2004 ◽  
Vol 13 (10) ◽  
pp. 2329-2335
Author(s):  
ANDREW CHAMBLIN ◽  
JOSHUA ERLICH
Keyword(s):  
Black Holes ◽  
Gravitational Field ◽  
Degrees Of Freedom ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Gravitational Entropy ◽  
Entropy Bound

Just as gravitons can carry energy, they can also be used to transmit information. It follows that an entropy should be associated with gravitational degrees of freedom, independent of the presence or absence of black holes. In this essay, we discuss how one might count gravitational entropy given a classical gravitational field. Our suggestion is motivated by a derivation of the covariant entropy bound in which a gravitational term appears naturally.

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