scholarly journals Thermodynamics of scale-dependent Friedmann equations

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Pedro Bargueño ◽  
Ernesto Contreras ◽  
Ángel Rincón
Keyword(s):  
Black Hole ◽  
Entropy Production ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Time Varying ◽  
Equilibrium Thermodynamics ◽  
Production Term ◽  
Friedmann Equations ◽  
Matter Energy

AbstractIn this work, the role of a time-varying Newton constant under the scale-dependent approach is investigated in the thermodynamics of the Friedman equations. In particular, we show that the extended Friedman equations can be derived either from equilibrium thermodynamics when the non-matter energy momentum tensor is interpreted as a fluid or from non-equilibrium thermodynamics when an entropy production term, which depends on the time-varying Newton constant, is included. Finally, a comparison between black hole and cosmological thermodynamics in the framework of scale-dependent gravity is briefly discussed.

scholarly journals COVARIANT ANOMALIES, HORIZONS AND HAWKING RADIATION

2008 ◽  
Vol 17 (13n14) ◽  
pp. 2539-2542 ◽  
Author(s):  
RABIN BANERJEE
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Hawking Radiation ◽  
Crucial Role ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Diffeomorphism Symmetry

Hawking radiation is obtained from anomalies resulting from a breaking of diffeomorphism symmetry near the event horizon of a black hole. Such anomalies, manifested as a nonconservation of the energy–momentum tensor, occur in two different forms — covariant and consistent. The crucial role of covariant anomalies near the horizon is revealed, since this is the only input required to obtain the Hawking flux, thereby highlighting the universality of this effect. A brief description of the application of this method to obtain thermodynamic entities like entropy or temperature is provided.

scholarly journals The thermodynamic theory of black holes

1977 ◽  
Vol 353 (1675) ◽  
pp. 499-521 ◽  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Energy Momentum Tensor ◽  
Heat Bath ◽  
Naked Singularity ◽  
Momentum Tensor ◽  
Thermodynamic Theory ◽  
Model Systems ◽  
Quantum Energy ◽  
Third Law Of Thermodynamics

The thermodynamic theory underlying black hole processes is developed in detail and applied to model systems. I t is found that Kerr-Newman black holes undergo a phase transition at a = 0.68 M or Q = 0.86 M , where the heat capacity has an infinite discontinuity. Above the transition values the specific heat is positive, permitting isothermal equilibrium with a surrounding heat bath. Simple processes and stability criteria for various black hole situations are investigated. The limits for entropieally favoured black hole formation are found. The Nernst conditions for the third law of thermodynamics are not satisfied fully for black holes. There is no obvious thermodynamic reason why a black hole may not be cooled down below absolute zero and converted into a naked singularity. Quantum energy-momentum tensor calculations for uncharged black holes are extended to the Reissner-Nordstrom case, and found to be fully consistent with the thermodynamic picture for Q < M . For Q > M the model predicts that ‘naked’ collapse also produces radiation, with such intensity that the collapsing matter is entirely evaporated away before a naked singularity can form.

N=2 SUPERCONFORMAL INTERACTING BOSONIC MODELS

1992 ◽  
Vol 07 (04) ◽  
pp. 345-356 ◽  
Author(s):  
RON COHEN
Keyword(s):  
Free Energy ◽  
Energy Momentum Tensor ◽  
Central Charge ◽  
Oriented Graph ◽  
Momentum Tensor ◽  
Superconformal Algebra ◽  
Chiral Algebra ◽  
Bosonic Model ◽  
Coset Models

Bosonic representations of N=2 superconformal algebra are studied. We show that the free energy momentum tensor decomposes into an orthogonal sum of the interacting bosonic model (IBM) and a coset-like tensors. We define the notion of flags of models and show that the central charge does not decrease along the flags. We examine the conditions for an arbitrary un-oriented graph to form an IBM. We discuss several properties of the chiral algebra of these models and examine the role of the continuous parameters by studying an example. Finally we discuss the relations between these models and the N=2 superconformal coset models.

UNUSUAL HYDRODYNAMICS

1987 ◽  
Vol 02 (05) ◽  
pp. 1591-1615 ◽  
Author(s):  
V.A. BEREZIN
Keyword(s):  
Black Hole ◽  
Cosmological Model ◽  
Production Process ◽  
Particle Production ◽  
Energy Momentum Tensor ◽  
Equations Of Motion ◽  
Momentum Tensor ◽  
Point Of View ◽  
Modified Equations ◽  
Nonsingular Cosmological Model

A method for the phenomenological description of particle production is proposed. Correspondingly modified equations of motion and energy-momentum tensor are obtained. In order to illustrate this method we reconsider from the new point of view of (i) the C-field Hoyle-Narlikar cosmology, (ii) the influence of the particle production process on metric inside the event horizon of a charged black hole and (iii) a nonsingular cosmological model.

scholarly journals CANONICAL APPROACH TO 2D SUPERSYMMETRIC WZNW MODEL COUPLED TO SUPERGRAVITY

2002 ◽  
Vol 17 (29) ◽  
pp. 1923-1936 ◽  
Author(s):  
OLIVERA MIŠKOVIĆ ◽  
BRANISLAV SAZDOVIĆ
Keyword(s):  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Moody Algebra ◽  
Gauge Transformations ◽  
Local Gauge ◽  
Gauge Symmetries ◽  
Wznw Model ◽  
Canonical Approach ◽  
Explicit Expressions

Starting from the known representation of the Kac–Moody algebra in terms of the coordinates and momenta, we extend it to the representation of the super Kac–Moody and super Virasoro algebras. Then we use general canonical method to construct an action invariant under local gauge symmetries, where components of the super energy–momentum tensor L± and G± play the role of the diffeomorphisms and supersymmetry generators respectively. We obtain covariant extension of WZNW theory with respect to local supersymmetry as well as explicit expressions for gauge transformations.

scholarly journals On homogeneous and isotropic universe

2015 ◽  
Vol 30 (34) ◽  
pp. 1550186 ◽  
Author(s):  
M. O. Katanaev
Keyword(s):  
Vector Fields ◽  
Energy Momentum Tensor ◽  
Killing Vector ◽  
Momentum Tensor ◽  
Killing Vector Fields ◽  
Full System ◽  
Independent Functions ◽  
Definition Of ◽  
Usual Scale ◽  
Matter Energy

We give a simple example of spacetime metric, illustrating that homogeneity and isotropy of space slices at all moments of time is not obligatory lifted to a full system of six Killing vector fields in spacetime, thus it cannot be interpreted as a symmetry of a four-dimensional metric. The metric depends on two arbitrary and independent functions of time. One of these functions is the usual scale factor. The second function cannot be removed by coordinate transformations. We prove that it must be equal to zero, if the metric satisfies Einstein’s equations and the matter energy–momentum tensor is homogeneous and isotropic. A new, equivalent, definition of homogeneous and isotropic spacetime is given.

scholarly journals A NEAR HORIZON CFT DUAL FOR KERR–NEWMAN AdS

2011 ◽  
Vol 26 (18) ◽  
pp. 3077-3090 ◽  
Author(s):  
BRADLY K. BUTTON ◽  
LEO RODRIGUEZ ◽  
CATHERINE A. WHITING ◽  
TUNA YILDIRIM
Keyword(s):  
Black Hole ◽  
Energy Momentum Tensor ◽  
Central Charge ◽  
Virasoro Algebra ◽  
Momentum Tensor ◽  
Two Dimensional ◽  
S Wave ◽  
One Dimensional ◽  
Conformal Field ◽  
Asymptotic Symmetries

We show that the near horizon regime of a Kerr–Newman AdS (KNAdS) black hole, given by its two-dimensional analogue a là Robinson and Wilczek (Phys. Rev. Lett.95, 011303 (2005)), is asymptotically AdS2 and dual to a one-dimensional quantum conformal field theory (CFT). The s-wave contribution of the resulting CFT's energy–momentum tensor together with the asymptotic symmetries, generate a centrally extended Virasoro algebra, whose central charge reproduces the Bekenstein–Hawking entropy via Cardy's formula. Our derived central charge also agrees with the near extremal Kerr/CFT correspondence (Phys. Rev. D80, 124008 (2009)) in the appropriate limits. We also compute the Hawking temperature of the KNAdS black hole by coupling its Robinson and Wilczek two-dimensional analogue (RW2DA) to conformal matter.

On the origin of black hole evaporation radiation

1976 ◽  
Vol 351 (1664) ◽  
pp. 129-139 ◽  
Keyword(s):  
Black Hole ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Static Vacuum ◽  
Black Hole Evaporation ◽  
A Value ◽  
Special Case ◽  
Collapse Process

The physical basis underlying the black hole evaporation process is clarified by a calculation of the expectation value of the energy-momentum tensor for a massless scalar field in a completely general two dimensional collapse scenario. It is found that radiation is produced inside the collapsing matter which propagates both inwards and outwards. The ingoing com­ponent eventually emerges from the star after travelling through the centre. The outgoing energy flux appears at infinity as the evaporation radiation discovered by Hawking. At late times, outside the star, the former component fades out exponentially, and the latter component approaches a value which is independent of the details of the collapse process. In the special case of a collapsing hollow, thin shell of matter, all the radiation is produced at the shell. These results are independent of regularization ambiguities, which enter only the static vacuum polariza­tion terms in the energy-momentum tensor. The significance of an earlier remark about black hole explosions is discussed in the light of these results.

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