Einstein's equations as a thermodynamic identity: The cases of stationary axisymmetric horizons and evolving spherically symmetric horizons

Kothawala, Dawood; Sarkar, Sudipta; Padmanabhan, Τ.

doi:10.1016/j.physletb.2007.07.021

Cited by 161 publications

(150 citation statements)

References 35 publications

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“…the field equations become T dS = dE + P dV ) continues to hold for a very wide class of theories! In the more general class of theories, one can define a natural entropy for the horizon called the Wald entropy [17] and we again get the same result with correct Wald entropy (for a sample of results see [18][19][20][21][22][23][24][25][26]). …”

Section: Gravitational Field Equations As a Thermodynamic Identitysupporting

confidence: 54%

Emergent perspective of gravity and dark energy

Padmanabhan¹

2012

Res. Astron. Astrophys.

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117

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There is sufficient amount of internal evidence in the nature of gravitational theories to indicate that gravity is an emergent phenomenon like, e.g, elasticity. Such an emergent nature is most apparent in the structure of gravitational dynamics. It is, however, possible to go beyond the field equations and study the space itself as emergent in a well-defined manner in (and possibly only in) the context of cosmology. In the first part of this review, I describe various pieces of evidence which show that gravitational field equations are emergent. In the second part, I describe a novel way of studying cosmology in which I interpret the expansion of the universe as equivalent to the emergence of space itself. In such an approach, the dynamics evolves towards a state of holographic equipartition, characterized by the equality of number of bulk and surface degrees of freedom in a region bounded by the Hubble radius. This principle correctly reproduces the standard evolution of a Friedmann universe. Further, (a) it demands the existence of an early inflationary phase as well as late time acceleration for its successful implementation and (b) allows us to link the value of late time cosmological constant to the e-folding factor during inflation.

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Section: Gravitational Field Equations As a Thermodynamic Identitysupporting

confidence: 54%

Emergent perspective of gravity and dark energy

Padmanabhan¹

2012

Res. Astron. Astrophys.

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117

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“…Recently, this scenario has been extensively investigated in various approaches [38][39][40][41][42][43][44][45][46][47][48]. In particular, based on the assumption that the gravitational theory can be described by entropy force [49], which has been widely interested by many theorists [40,[50][51][52][53][54][55][56][57][58][59][60][61][62][63], the authors in [40] proposed that an interesting setup was that the modified dispersion relation prevented the energy density of the matter contents from diverging at high energy level such that the modified Friedmann equation with the bouncing effect can be derived successfully from the Clausius relation, where the singularity of the corresponding spacetime was free.…”

Section: Introductionmentioning

confidence: 99%

Bouncing universe with modified dispersion relation

Pan¹,

Huang²

2016

Gen Relativ Gravit

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In this paper, employing the modified dispersion relation, we have derived the general modified Friedmann equations and the corresponding modified entropy relations for the FriedmannRobertson-Walker (FRW) Universe. In this setup, we find that when the big bounce happens, its energy scale and its corresponding modified entropy behavior are sensitive to the value of k.In contrast to the previous work with k = 0, our work mainly demonstrates that the bouncing behavior for the closed Universe with k = 1 appears at the normal energy limit of the modified dispersion relation introduced, and when bouncing phenomenon is in presence, its modified entropy is just equal to zero. Surprisingly, when k = −1, the bouncing behavior is in absence. * Electronic address: wjpan˙zhgkxy@163.com † Electronic address: ychuang@bjut.edu.cn

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“…(2) as a suitable definition for temperature [53][54][55]. Indeed, it seems that this similarity is much more than a mere resemblance [53][54][55][56][57][58][59][60][61][62][63][64][65].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of universe with a varying dark energy component

Ebadi

Moradpour

2015

Int. J. Mod. Phys. D

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We consider a FRW universe filled by a dark energy candidate together with other possible sources which may include the baryonic and non-baryonic matters. Thereinafter, we consider a situation in which the cosmos sectors do not interact with each other. By applying the unified first law of thermodynamics on the apparent horizon of the FRW universe, we show that the dark energy candidate may modify the apparent horizon entropy and thus the Bekenstein limit. Moreover, we generalize our study to the models in which the cosmos sectors have a mutual interaction. Our final result indicates that the mutual interaction between the cosmos sectors may add an additional term to the apparent horizon entropy leading to modify the Bekenstein limit. Relationships with previous works have been addressed throughout the paper. Finally, we investigate the validity of the second law of thermodynamics and its generalized form in the interacting and non-interacting cosmoses.

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Einstein's equations as a thermodynamic identity: The cases of stationary axisymmetric horizons and evolving spherically symmetric horizons

Cited by 161 publications

References 35 publications

Emergent perspective of gravity and dark energy

Emergent perspective of gravity and dark energy

Bouncing universe with modified dispersion relation

Thermodynamics of universe with a varying dark energy component

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