BRANE WORLD DYNAMICS AND ADIABATIC MATTER CREATION

2006 ◽  
Vol 15 (03) ◽  
pp. 321-334 ◽  
Author(s):  
P. GOPAKUMAR ◽  
G. V. VIJAYAGOVINDAN
Keyword(s):  
Energy Density ◽  
Open Systems ◽  
Brane World ◽  
Creation Process ◽  
Brane Worlds ◽  
Matter Creation ◽  
Standard Scenario ◽  
Brane Models ◽  
The Universe ◽  
Creation Rate

We treat the adiabatic matter creation process in various three-brane models by applying the thermodynamics of open systems. The matter creation rate is found to affect the evolution of the scale factor and energy density of the universe. We find a modification at the early stages of cosmic dynamics. In GB and RS brane worlds, by choosing appropriate parameters we obtain the standard scenario, while the warped DGP model has different solutions. During later stages, since matter creation is negligible, the evolution reduces to FRW expansion, in the RS and GB models.

COSMOLOGY WITH ADIABATIC MATTER CREATION

1994 ◽  
Vol 03 (01) ◽  
pp. 327-330 ◽  
Author(s):  
WINFRIED ZIMDAHL ◽  
DIEGO PAVÓN
Keyword(s):  
Stability Analysis ◽  
Energy Density ◽  
Early Universe ◽  
Particle Production ◽  
De Sitter ◽  
Matter Creation ◽  
Production Processes ◽  
Density Perturbations ◽  
Creation Rate

The standard Friedmann-Lemaître-Robertson-Walker (FLRW) model is modified to include particle production processes. The influence of these processes on the dynamics of the early Universe is investigated. We argue that a sufficiently high creation rate may give rise to an inflationary period. A stability analysis about this background yields growing energy density perturbations during the de Sitter stage.

ON FRIEDMANN'S EQUATION IN BRANE-WORLDS

2002 ◽  
Vol 17 (29) ◽  
pp. 4341-4348 ◽  
Author(s):  
M. D. MAIA ◽  
E. M. MONTE ◽  
J. M. F. MAIA
Keyword(s):  
Radial Direction ◽  
Extrinsic Curvature ◽  
Brane World ◽  
Accelerated Expansion ◽  
Minimal Set ◽  
Brane Worlds ◽  
Expansion Of The Universe ◽  
The Universe

The modified Friedmann's equation is derived from the minimal set of postulates in the brane-world program. It is shown that the recently observed accelerated expansion of the universe can be explained in terms of the extrinsic curvature of the universe along the radial direction.

scholarly journals Cosmological constraints on entropic cosmology with matter creation

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Hussain Gohar ◽  
Vincenzo Salzano
Keyword(s):  
Energy Exchange ◽  
Force Model ◽  
Observational Constraints ◽  
Entropic Force ◽  
Cosmological Constraints ◽  
Matter Creation ◽  
Functional Forms ◽  
Temperature Parameter ◽  
The Universe ◽  
Creation Rate

AbstractWe investigate entropic force cosmological models with the possibility of matter creation and energy exchange between the bulk and the horizon of a homogeneous and isotropic flat Universe. We consider three different kinds of entropy, Bekenstein’s, the non-extensive Tsallis–Cirto’s, and the quartic entropy, plus some phenomenological functional forms for matter creation rate to model different entropic force models and put the observational constraints on them. We show that while most of them are indistinguishable from a standard $$\Lambda $$ Λ CDM scenario, the Bekenstein entropic force model with a matter creation rate proportional to the Hubble parameter is statistically highly favored over $$\Lambda $$ Λ CDM. As a general result, we also find that both the Hawking temperature parameter $$\gamma $$ γ , which relates the energy exchange between the bulk and the boundary of the Universe, and the matter creation rate $$\Gamma (t)$$ Γ ( t ) , must be very small to reproduce observational data.

scholarly journals Quintessence behavior via matter creation cosmology

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
C. P. Singh ◽  
Ajay Kumar
Keyword(s):  
Open Systems ◽  
State Parameter ◽  
Information Criterion ◽  
Irreversible Processes ◽  
Model Parameters ◽  
Alternative Theory ◽  
Distance Modulus ◽  
Field Equations ◽  
Matter Creation ◽  
The Universe

Abstract We study the matter creation cosmology as an alternative theory to explain the dark energy phenomena. We discuss the matter-dominated Universe in a flat Friedmann-Robertson-Walker line element by adopting the thermodynamics of open systems, in which the matter creation irreversible processes may take place at a cosmological scale. We propose a new form of the matter creation rate, $$\varGamma =3\alpha H_0+3\beta H+3\gamma \; \frac{\ddot{a}}{{\dot{a}}}$$Γ=3αH0+3βH+3γa¨a˙, which generalizes some of the previous models in the literature. Exact solutions of the field equations are found and discussed the evolution of the Universe. Constraints on the model parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the Supernova distance modulus data, observational measurements of Hubble parameter, Baryon acoustic oscillation data. The trajectories of the evolution of the scale factor, deceleration parameter and equation of state parameter are plotted by using best-fit values of the parameters. It is observed that the model shows accelerating behavior and behaves quintessence like ($$\omega >-1$$ω>-1). The age of the Universe is obtained which is in good agreement with $$\varLambda $$ΛCDM model. We examine the model using two independent diagnostic parameters, namely statefinder and $$\textit{Om}$$Om. We apply Akaike information criterion (AIC) and Bayesian information criterion (BIC) to discriminate the model based on the penalization associated to the number of parameters. The analysis shows that the model has close resemblance to the $$\varLambda CDM$$ΛCDM cosmology. We also discuss the thermodynamics of the model and find that the model satisfies the generalized second law of thermodynamics with certain constraints.

scholarly journals Dynamical system analysis of FLRW models with Modified Chaplygin gas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ali Osman Yılmaz ◽  
Ertan Güdekli
Keyword(s):  
Dynamical System ◽  
Equation Of State ◽  
Energy Density ◽  
System Analysis ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
State Spaces ◽  
The Universe ◽  
Matter Energy ◽  
Far Future

AbstractWe investigate Friedmann–Lamaitre–Robertson–Walker (FLRW) models with modified Chaplygin gas and cosmological constant, using dynamical system methods. We assume $$p=(\gamma -1)\mu -\dfrac{A}{\mu ^\alpha }$$ p = ( γ - 1 ) μ - A μ α as equation of state where $$\mu$$ μ is the matter-energy density, p is the pressure, $$\alpha$$ α is a parameter which can take on values $$0<\alpha \le 1$$ 0 < α ≤ 1 as well as A and $$\gamma$$ γ are positive constants. We draw the state spaces and analyze the nature of the singularity at the beginning, as well as the fate of the universe in the far future. In particular, we address the question whether there is a solution which is stable for all the cases.

scholarly journals de Sitter in non-supersymmetric string theories: no-go theorems and brane-worlds

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Ivano Basile ◽  
Stefano Lanza
Keyword(s):  
Flux Compactifications ◽  
Cosmological Constant ◽  
Dimensional Reduction ◽  
Brane World ◽  
De Sitter ◽  
Top Down ◽  
Brane Worlds ◽  
Concrete Realization ◽  
String Models ◽  
String Theories

Abstract We study de Sitter configurations in ten-dimensional string models where supersymmetry is either absent or broken at the string scale. To this end, we derive expressions for the cosmological constant in general warped flux compactifications with localized sources, which yield no-go theorems that extend previous works on supersymmetric cases. We frame our results within a dimensional reduction and connect them to a number of Swampland conjectures, corroborating them further in the absence of supersymmetry. Furthermore, we construct a top-down string embedding of de Sitter brane-world cosmologies within unstable anti-de Sitter landscapes, providing a concrete realization of a recently revisited proposal.

scholarly journals Dark Energy Density in Brane World

2005 ◽  
Vol 22 (4) ◽  
pp. 816-819 ◽  
Author(s):  
Wen Hai-Bao ◽  
Huang Xin-Bing
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Brane World ◽  
Dark Energy Density

Heuristic determination of the cosmological constant

2021 ◽  
pp. 2150114
Author(s):  
Manuel Urueña Palomo ◽  
Fernando Pérez Lara
Keyword(s):  
Field Theory ◽  
Energy Density ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Fundamental Constants ◽  
Quantum Field ◽  
Brute Force ◽  
Expansion Of The Universe ◽  
The Universe

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in physics performing a dimensional analysis, in search of an equation resulting in the measured energy density of the vacuum or cosmological constant that is assumed to cause the accelerated expansion of the universe.

DARK GEOMETRY

2004 ◽  
Vol 13 (10) ◽  
pp. 2275-2279 ◽  
Author(s):  
J. A. R. CEMBRANOS ◽  
A. DOBADO ◽  
A. L. MAROTO
Keyword(s):  
Dark Matter ◽  
Extra Dimensions ◽  
Degrees Of Freedom ◽  
Planck Scale ◽  
Point Of View ◽  
Missing Mass ◽  
Brane Worlds ◽  
Mass Problem ◽  
Extra Space ◽  
The Universe

Extra-dimensional theories contain additional degrees of freedom related to the geometry of the extra space which can be interpreted as new particles. Such theories allow to reformulate most of the fundamental problems of physics from a completely different point of view. In this essay, we concentrate on the brane fluctuations which are present in brane-worlds, and how such oscillations of the own space–time geometry along curved extra dimensions can help to resolve the Universe missing mass problem. The energy scales involved in these models are low compared to the Planck scale, and this means that some of the brane fluctuations distinctive signals could be detected in future colliders and in direct or indirect dark matter searches.

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