scholarly journals Supersymmetric large extra dimensions and the cosmological constant problem

2006 ◽  
Vol 84 (6-7) ◽  
pp. 463-472 ◽  
Author(s):  
C P Burgess
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Present Status ◽  
Extra Dimensions ◽  
Large Extra Dimensions ◽  
Cosmological Constant Problem ◽  
Dark Energy Density ◽  
Higher Dimensional

This article briefly summarizes and reviews the motivations for — and the present status of — the proposal that the small size of the observed Dark Energy density can be understood in terms of the dynamical relaxation of two large extra dimensions within a supersymmetric higher dimensional theory.PACS Nos.: 31.15.Pf, 31.30.Jv, 32.10.Hq

FRW viscous modified cosmic Chaplygin gas cosmology in the presence of cosmological constant

2019 ◽  
Vol 16 (09) ◽  
pp. 1950141 ◽  
Author(s):  
G. S. Khadekar ◽  
Aina Gupta ◽  
Kalpana Pande
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Chaplygin Gas ◽  
Frw Universe ◽  
Dark Energy Density ◽  
Linear Combinations ◽  
Linear Differential ◽  
The Stability ◽  
Cardassian Universe

In this paper, we study viscous Modified Cosmic Chaplygin Gas (MCCG) in the presence of cosmological constant in flat FRW universe. We assume that bulk viscosity [Formula: see text] and cosmological constant [Formula: see text] are the linear combinations of two terms, one is constant and other is a function of dark energy density [Formula: see text]. In this framework, we solve the non-linear differential equation analytically and numerically and obtain time dependent dark energy density. We also consider two separate cases of early and late universe and discussed the evolution of dark energy density. We investigate the effect of viscosity and cosmological constant to the evolution of universe and discuss the stability of the model by square of speed of sound. Finally, we compare our model with Cardassian universe.

scholarly journals SUPERNOVA Ia AND GALAXY CLUSTER GAS MASS FRACTION CONSTRAINTS ON DARK ENERGY

2006 ◽  
Vol 21 (29) ◽  
pp. 2197-2204 ◽  
Author(s):  
KYLE M. WILSON ◽  
GANG CHEN ◽  
BHARAT RATRA
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Mass Fraction ◽  
Galaxy Cluster ◽  
Apparent Magnitude ◽  
Model Parameters ◽  
Dark Energy Density ◽  
Energy Models ◽  
Fraction Versus

We use the Riess et al. (2004)1 supernova Ia apparent magnitude versus redshift data and the Allen et al. (2004)2 galaxy cluster gas mass fraction versus redshift data to constrain dark energy models. These data provide complementary constraints that when combined together significantly restrict model parameters and favor slowly-evolving dark energy density models, close to the Einstein cosmological constant limit of dark energy.

scholarly journals DARK ENERGY DENSITY IN MODELS WITH SPLIT SUPERSYMMETRY AND DEGENERATE VACUA

2012 ◽  
Vol 27 (11) ◽  
pp. 1250063 ◽  
Author(s):  
C. FROGGATT ◽  
R. NEVZOROV ◽  
H. B. NIELSEN
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Susy Breaking ◽  
Vacuum Energy Density ◽  
Dark Energy Density ◽  
Hidden Sector ◽  
Split Supersymmetry ◽  
Breaking Scale

In N = 1 supergravity supersymmetric and nonsupersymmetric Minkowski vacua originating in the hidden sector can be degenerate. In the supersymmetric phase in flat Minkowski space, nonperturbative supersymmetry breakdown may take place in the observable sector, inducing a nonzero and positive vacuum energy density. Assuming that such a supersymmetric phase and the phase in which we live are degenerate, we estimate the value of the cosmological constant. We argue that the observed value of the dark energy density can be reproduced in the split SUSY scenario of SUSY breaking if the SUSY breaking scale is of order of 1010 GeV.

scholarly journals SOME CONSEQUENCES OF DARK ENERGY DENSITY VARYING EXPONENTIALLY WITH SCALE FACTOR

2005 ◽  
Vol 20 (36) ◽  
pp. 2805-2818
Author(s):  
SANIL UNNIKRISHNAN ◽  
T. R. SESHADRI
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Scale Factor ◽  
Dark Energy Density ◽  
Phantom Field

In this paper we have explored the consequences of a model of dark energy with its energy density varying exponentially with the scale factor. We first consider the model with ρϕ∝eκa, where κ is a constant. This is a kind of generalization of the cosmological constant model with κ=0. We show that such an exponentially varying dark energy density with the scale factor naturally leads to an equivalent phantom field. We also consider a model with ρϕ∝eκ/a and show that this also naturally leads to an equivalent phantom field.

scholarly journals Can a Chameleon Field Be Identified with Quintessence?

Universe ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. 221
Author(s):  
A. N. Ivanov ◽  
M. Wellenzohn
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Energy Density ◽  
Cosmological Constant ◽  
Gravitational Theory ◽  
Einstein Equations ◽  
Late Time ◽  
Dark Energy Density ◽  
Full Extent ◽  
Energy Dynamics

In the Einstein–Cartan gravitational theory with the chameleon field, while changing its mass independently of the density of its environment, we analyze the Friedmann–Einstein equations for the Universe’s evolution with the expansion parameter a being dependent on time only. We analyze the problem of an identification of the chameleon field with quintessence, i.e., a canonical scalar field responsible for dark energy dynamics, and for the acceleration of the Universe’s expansion. We show that since the cosmological constant related to the relic dark energy density is induced by torsion (Astrophys. J.2016, 829, 47), the chameleon field may, in principle, possess some properties of quintessence, such as an influence on the dark energy dynamics and the acceleration of the Universe’s expansion, even in the late-time acceleration, but it cannot be identified with quintessence to the full extent in the classical Einstein–Cartan gravitational theory.

Comments on the Cosmological Constant Problem and How it Can be Solved

1997 ◽  
Vol 06 (05) ◽  
pp. 643-648 ◽  
Author(s):  
Paul S. Wesson
Keyword(s):  
General Relativity ◽  
Energy Density ◽  
Cosmological Constant ◽  
Dimensional Theory ◽  
Cosmological Constant Problem ◽  
Higher Dimensional ◽  
Theory Of Gravity

The problem of disparate estimates of the energy density of the vacuum can be solved, at least in principle, by reducing a higher-dimensional theory of gravity to general relativity and a local cosmological "constant."

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

scholarly journals Limits on decaying dark energy density models from the CMB temperature–redshift relation

2010 ◽  
Vol 43 (4) ◽  
pp. 1083-1093 ◽  
Author(s):  
Philippe Jetzer ◽  
Denis Puy ◽  
Monique Signore ◽  
Crescenzo Tortora
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Dark Energy Density ◽  
Cmb Temperature
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