scholarly journals On Gravitational Entropy of de Sitter Universe

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
S. C. Ulhoa ◽  
E. P. Spaniol
Keyword(s):  
Phase Transition ◽  
Cosmological Constant ◽  
De Sitter Space ◽  
Teleparallel Gravity ◽  
Space Time ◽  
Gravitational Energy ◽  
De Sitter ◽  
First Law Of Thermodynamics ◽  
Gravitational Entropy ◽  
De Sitter Universe

The paper deals with the calculation of the gravitational entropy in the context of teleparallel gravity for de Sitter space-time. In such a theory it is possible to define gravitational energy and pressure; thus we use those expressions to construct the gravitational entropy. We use the temperature as a function of the cosmological constant and write the first law of thermodynamics from which we obtain the entropy. In the limit Λ≪1 we find that the entropy is proportional to volume, for a specific temperature’s choice; we find that ΔS≥0 as well. We also identify a phase transition in de Sitter space-time by analyzing the specific heat.

THERMODYNAMICS OF de SITTER SPACE–TIME IN YORK'S FORMALISM

2001 ◽  
Vol 16 (23) ◽  
pp. 1487-1492 ◽  
Author(s):  
BO-BO WANG ◽  
CHAO-GUANG HUANG
Keyword(s):  
Black Holes ◽  
Cosmological Constant ◽  
Path Integral ◽  
De Sitter Space ◽  
Space Time ◽  
Integral Approach ◽  
De Sitter ◽  
First Law Of Thermodynamics ◽  
Path Integral Approach ◽  
Thermodynamics Of Black Holes

The York's formalism of path-integral approach to the thermodynamics of black holes is applied to de Sitter space–time. The first law of thermodynamics for de Sitter space–time is given, which includes a "work term" with respect to the cosmological constant.

scholarly journals Phase Transition and Entropy Force between Two Horizons in (n+2)-Dimensional de Sitter Space

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Yang Zhang ◽  
Wen-qi Wang ◽  
Yu-bo Ma ◽  
Jun Wang
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Physical Mechanism ◽  
De Sitter Space ◽  
Space Time ◽  
Thermodynamic Quantities ◽  
De Sitter ◽  
Time Dimension ◽  
Cosmic Expansion

In this paper, the effect of the space-time dimension on effective thermodynamic quantities in (n+2)-dimensional Reissner-Nordstrom-de Sitter space has been studied. Based on derived effective thermodynamic quantities, conditions for the phase transition are obtained. The result shows that the accelerating cosmic expansion can be attained by the entropy force arisen from the interaction between horizons of black holes and our universe, which provides a possible way to explain the physical mechanism for the accelerating cosmic expansion.

THE DE SITTER UNIVERSE MODELS

1995 ◽  
Vol 04 (01) ◽  
pp. 115-159 ◽  
Author(s):  
E. ERIKSEN ◽  
Ø. GRØN
Keyword(s):  
Bianchi Type ◽  
De Sitter Space ◽  
Space Time ◽  
Analytic Extension ◽  
Coordinate Transformations ◽  
De Sitter ◽  
Type Iii ◽  
Dimensional Spacetime ◽  
De Sitter Universe ◽  
Universe Models

The kinematical properties of the de Sitter space-time are reviewed and investigated. The properties of the static sections are clarified. A deduction of the analytic extension, analogous to that of Kruskal and Szekeres for the Schwarzschild space-time, of the static section to the region outside the horizon is given. The representation of the de Sitter space-time as a four-dimensional hyperboloid in Minkowskian five-dimensional spacetime is reviewed. Coordinate transformations between different sections of the de Sitter space-time are found. By means of the transformation formulae the different sections are mapped onto each other in space-time diagrams. These mappings are interpreted kinematically. We have aimed at providing, whenever possible, an intuitive understanding of the kinematical properties of the different sections, and how they are interrelated. Among others we present real coordinate transformations between the static and the three Robertson-Walker sections of the de Sitter space-time on one hand and the vacuum dominated Bianchi type-III model on the other hand. These transformations are used to map the path of a typical Bianchi type-III reference particle into the static and the Robertson-Walker sections.

scholarly journals LOCAL OBSERVED TIME AND REDSHIFT IN CURVED SPACE–TIME

2001 ◽  
Vol 16 (21) ◽  
pp. 1385-1393 ◽  
Author(s):  
SZE-SHIANG FENG
Keyword(s):  
Cosmological Constant ◽  
Time Scale ◽  
Space Time ◽  
Local Observable ◽  
Length Scale ◽  
De Sitter ◽  
Perfect Agreement ◽  
Curved Space ◽  
De Sitter Universe ◽  
Changing Rate

Using the observed time and spatial intervals defined originally by Einstein and the observational frame in the vierbein formalism, we propose that in curved space–time, for a wave received in laboratories, the observed frequency is the changing rate of the phase of the wave relative to the local observable time scale and the momentum is the changing rate of the phase relative to the local observable spatial length scale. The case of Robertson–Walker universe is especially considered and the application to de Sitter universe results in a cosmological constant in perfect agreement with the observational data.

scholarly journals A REVIEW OF THE N-BOUND AND THE MAXIMAL MASS CONJECTURES USING NUT-CHARGED dS SPACE–TIMES

2004 ◽  
Vol 19 (24) ◽  
pp. 3987-4035 ◽  
Author(s):  
RICHARD CLARKSON ◽  
A. M. GHEZELBASH ◽  
ROBERT B. MANN
Keyword(s):  
Upper Bound ◽  
De Sitter Space ◽  
Space Time ◽  
Conserved Quantities ◽  
De Sitter ◽  
Cosmological Singularity ◽  
Gravitational Entropy ◽  
The Status ◽  
Maximal Mass ◽  
Gravitational Thermodynamics

The proposed dS/CFT correspondence remains an intriguing paradigm in the context of string theory. Recently it has motivated two interesting conjectures: the entropic N-bound and the maximal mass conjecture. The former states that there is an upper bound to the entropy in asymptotically de Sitter space–times, given by the entropy of pure de Sitter space. The latter states that any asymptotically de Sitter space–time cannot have a mass larger than the pure de Sitter case without inducing a cosmological singularity. Here we review the status of these conjectures and demonstrate their limitation. We first describe a generalization of gravitational thermodynamics to asymptotically de Sitter space–times, and show how to compute conserved quantities and gravitational entropy using this formalism. From this we proceed to a discussion of the N-bound and maximal mass conjectures. We then illustrate that these conjectures are not satisfied for certain asymptotically de Sitter space–times with NUT charge. We close with a presentation of explicit examples in various space–time dimensionalities.

scholarly journals THE GRAVITATIONAL ENERGY PROBLEM FOR COSMOLOGICAL MODELS IN TELEPARALLEL GRAVITY

2010 ◽  
Vol 19 (12) ◽  
pp. 1925-1935 ◽  
Author(s):  
S. C. ULHOA ◽  
J. F. DA ROCHA NETO ◽  
J. W. MALUF
Keyword(s):  
Average Energy ◽  
Teleparallel Gravity ◽  
Space Time ◽  
Gravitational Energy ◽  
Cosmological Models ◽  
De Sitter ◽  
Energy Problem ◽  
First Case ◽  
Einstein's Equation ◽  
Average Energy Density

We present a method to calculate the gravitational energy when asymptotic boundary conditions for the space–time are not given. This is the situation for most of the cosmological models. The expression for the gravitational energy is obtained in the context of the teleparallel equivalent of general relativity. We apply our method first to the Schwarzschild–de Sitter solution of Einstein's equation, and then to the Robertson–Walker universe. We show that in the first case our method leads to an average energy density of the vacuum space–time, and in the latter case the energy vanishes in the case of null curvature.

scholarly journals SPONTANEOUS DECAY OF THE EFFECTIVE COSMOLOGICAL CONSTANT

1998 ◽  
Vol 13 (07) ◽  
pp. 571-580 ◽  
Author(s):  
MURAT ÖZER ◽  
M. O. TAHA
Keyword(s):  
Cosmological Constant ◽  
De Sitter Space ◽  
Space Time ◽  
Time Dependent ◽  
Spontaneous Decay ◽  
Quantum Fields ◽  
De Sitter ◽  
Initial Value ◽  
Effective Time ◽  
Effective Cosmological Constant

We discuss the notion that quantum fields may induce an effective time-dependent cosmological constant which decays from a large initial value. It is shown that such cosmological models are viable in a non-de Sitter space–time.

Verifying the universe is another way to ds space-time

2021 ◽  
Author(s):  
Wen-Xiang Chen
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Cosmological Constant ◽  
Uncertainty Principle ◽  
De Sitter Space ◽  
Space Time ◽  
De Sitter ◽  
The Given ◽  
The Universe

In this paper, it is explained that the role of the cosmological constant in the De Sitter space is similar to that of the preset boundary conditions in the superradiation phenomenon. In the previous literature, superradiance at a given boundary condition can cause the uncertainty principle to be less extreme, and so the uncertainty principle to be less extreme without the given boundary condition, might be one way to prove that the universe is ds spacetime.

scholarly journals TWO-POINT FUNCTIONS AND QUANTUM FIELDS IN DE SITTER UNIVERSE

1996 ◽  
Vol 08 (03) ◽  
pp. 327-391 ◽  
Author(s):  
JACQUES BROS ◽  
UGO MOSCHELLA
Keyword(s):  
Plane Waves ◽  
Thermal Characterization ◽  
De Sitter Space ◽  
Space Time ◽  
Space Structure ◽  
Spectral Condition ◽  
De Sitter ◽  
Type Representation ◽  
Tube Domains ◽  
De Sitter Universe

We present a theory of general two-point functions and of generalized free fields in d-dimensional de Sitter space-time which closely parallels the corresponding Minkowskian theory. The usual spectral condition is now replaced by a certain geodesic spectral condition, equivalent to a precise thermal characterization of the corresponding “vacuum” states. Our method is based on the geometry of the complex de Sitter space-time and on the introduction of a class of holomorphic functions on this manifold, called perikernels, which reproduce mutatis mutandis the structural properties of the two-point correlation functions of the Minkowskian quantum field theory. The theory contains as basic elementary case the linear massive field models in their “preferred” representation. The latter are described by the introduction of de Sitter plane waves in their tube domains which lead to a new integral representation of the two-point functions and to a Fourier-Laplace type transformation on the hyperboloid. The Hilbert space structure of these theories is then analysed by using this transformation. In particular we show the Reeh-Schlieder property. For general two-point functions, a substitute to the Wick rotation is defined both in complex space-time and in the complex mass variable, and substantial results concerning the derivation of Källen-Lehmann type representation are obtained.

scholarly journals Instanton interaction in de Sitter space–time

2018 ◽  
Vol 33 (33) ◽  
pp. 1850200
Author(s):  
Dimitrios Metaxas
Keyword(s):  
Cosmological Constant ◽  
Decay Rate ◽  
De Sitter Space ◽  
Space Time ◽  
Tunneling Rate ◽  
Cosmological Horizon ◽  
De Sitter ◽  
Vacuum Decay ◽  
Background Space

Because of the presence of a cosmological horizon, the dilute instanton gas approximation used for the derivation of the Coleman–De Luccia tunneling rate in de Sitter space–time receives additional contributions due to the finite instanton separation. Here, I calculate the first corrections to the vacuum decay rate that arise from this effect and depend on the parameters of the theory and the cosmological constant of the background space–time.

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