scholarly journals ADIABATIC PARTICLE PRODUCTION WITH DECAYING Λ AND ANISOTROPIC UNIVERSE

2005 ◽  
Vol 14 (11) ◽  
pp. 1919-1925 ◽  
Author(s):  
SISIR BHANJA ◽  
SUBENOY CHAKRABORTY ◽  
UJJAL DEBNATH
Keyword(s):  
Cosmological Constant ◽  
Particle Production ◽  
Adiabatic Process ◽  
Anisotropic Universe ◽  
Anisotropic Model ◽  
Statefinder Parameters ◽  
Constant Energy ◽  
The Universe ◽  
Decaying Λ

Here we study an anisotropic model of the universe with constant energy per particle. A decaying cosmological constant and particle production in an adiabatic process are considered as the sources for the entropy. The statefinder parameters {r, s} are defined and their behavior are analyzed graphically in some cases.

THE ROLE OF A CHAMELEON FIELD IN AN ANISOTROPIC UNIVERSE WITH LOGAMEDIATE AND INTERMEDIATE SCENARIOS

2010 ◽  
Vol 25 (24) ◽  
pp. 4691-4701 ◽  
Author(s):  
SHUVENDU CHAKRABORTY ◽  
UJJAL DEBNATH
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Anisotropic Universe ◽  
Anisotropic Model ◽  
Scale Factors ◽  
Slow Roll ◽  
Energy Scalar ◽  
The Universe

In this work, we consider the Universe is being filled with matter composed of a chameleon-type dark energy scalar field. Employing a particular form of potential, we discuss the field's role in the accelerating phase of the Universe for an anisotropic model using the logamediate and intermediate forms of scale factors. The natures of statefinder and slow-roll parameters are discussed diagrammatically.

scholarly journals Study of a tachyonic field and its statefinder diagnostics in various scenarios of the anisotropic universe

2012 ◽  
Vol 90 (1) ◽  
pp. 97-105
Author(s):  
Chayan Ranjit ◽  
Surajit Chattopadhyay
Keyword(s):  
Dimensional Space ◽  
Anisotropic Universe ◽  
Statefinder Parameters ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Tachyonic Field ◽  
Dimensional Space Time ◽  
Walker Metric ◽  
The Universe ◽  
Friedmann Robertson Walker

In the present work, we have considered N-dimensional Einstein field equations in which four-dimensional space–time is described by a Friedmann–Robertson–Walker metric and the extra d-dimensions by an Euclidean metric. By considering the universe to be filled with a tachyonic field we have reconstructed the potential V([Formula: see text]) corresponding to the field reconstructions in an anisotropic universe under emergent – power law, emergent–intermediate, emergent–logamediate, and logamediate–intermediate scenarios. The statefinder parameters have been investigated in all of said scenarios.

Cosmological constant

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Vacuum Fluctuations ◽  
Present Epoch ◽  
Modify Gravity ◽  
Expansion Of The Universe ◽  
The Universe

The contribution of vacuum fluctuations to the cosmological constant is reconsidered studying the dependence on the used regularisation scheme. Then alternative explanations for the observed accelerated expansion of the universe in the present epoch are introduced which either modify gravity or add a new component of matter, dubbed dark energy. The chapter closes with some comments on attempts to quantise gravity.

A special anisotropic model of the universe (II)

1989 ◽  
Vol 21 (9) ◽  
pp. 967-970 ◽  
Author(s):  
Marcelo Samuel Berman ◽  
M. M. Som
Keyword(s):  
Anisotropic Model ◽  
The Universe

INFLATION, QUINTESSENCE PROBLEM AND VARYING SPEED OF LIGHT

2002 ◽  
Vol 17 (05) ◽  
pp. 295-302
Author(s):  
SUBENOY CHAKRABORTY
Keyword(s):  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Speed Of Light ◽  
Expansion Of The Universe ◽  
The Universe

In this paper it is shown that the present accelerated expansion of the Universe can be explained only by considering variation of the speed of light, without taking into account the cosmological constant or quintessence matter.

scholarly journals ANISOTROPIC COMPACT STARS WITH VARIABLE COSMOLOGICAL CONSTANT

2012 ◽  
Vol 21 (13) ◽  
pp. 1250088 ◽  
Author(s):  
SK. MONOWAR HOSSEIN ◽  
FAROOK RAHAMAN ◽  
JAYANTA NASKAR ◽  
MEHEDI KALAM ◽  
SAIBAL RAY
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Compact Star ◽  
Compact Stars ◽  
Radial Dependence ◽  
Regularity Conditions ◽  
Variable Cosmological Constant ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Surface Redshift

Recently, the small value of the cosmological constant and its ability to accelerate the expansion of the universe is of great interest. We discuss the possibility of forming of anisotropic compact stars from this cosmological constant as one of the competent candidates of dark energy. For this purpose, we consider the analytical solution of Krori and Barua metric. We take the radial dependence of cosmological constant and check all the regularity conditions, TOV equations, stability and surface redshift of the compact stars. It has been shown as conclusion that this model is valid for any compact star and we have cited 4U 1820-30 as a specific example of that kind of star.

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.

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