scholarly journals Nonlinear multidimensional cosmological models with form fields: Stabilization of extra dimensions and the cosmological constant problem

2003 ◽  
Vol 68 (4) ◽  
Author(s):  
U. Günther ◽  
P. Moniz ◽  
A. Zhuk
Keyword(s):  
Cosmological Constant ◽  
Extra Dimensions ◽  
Cosmological Models ◽  
Cosmological Constant Problem ◽  
Multidimensional Cosmological Models

scholarly journals A COVARIANT ENTROPY BOUND CONJECTURE ON THE DYNAMICAL HORIZON

2008 ◽  
Vol 17 (13n14) ◽  
pp. 2467-2474 ◽  
Author(s):  
SONG HE ◽  
HONGBAO ZHANG
Keyword(s):  
Black Holes ◽  
Cosmological Constant ◽  
Upper Bound ◽  
Supermassive Black Holes ◽  
Cosmological Models ◽  
Anthropic Principle ◽  
Holographic Principle ◽  
Cosmological Constant Problem ◽  
Entropy Contribution ◽  
Entropy Bound

We propose, as a compelling pattern for the holographic principle, a covariant entropy bound conjecture for more general dynamical horizons. Then we apply our conjecture to ΛCDM cosmological models, where we find that it imposes a novel upper bound, 10-90, on the cosmological constant for our own universe by taking into account the dominant entropy contribution from supermassive black holes, which thus provides an alternative macroscopic perspective for understanding the long-standing cosmological constant problem. As an intriguing implication of this conjecture, we also discuss the possible profound relation between the present cosmological constant, the origin of mass, and the anthropic principle.

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

scholarly journals From de Sitter to de Sitter: Decaying Vacuum Models as a Possible Solution to the Main Cosmological Problems

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
G. J. M. Zilioti ◽  
R. C. Santos ◽  
J. A. S. Lima
Keyword(s):  
Cosmological Constant ◽  
Large Class ◽  
First Principles ◽  
Cosmological Models ◽  
Late Time ◽  
De Sitter ◽  
Cosmological Constant Problem ◽  
Coincidence Problem ◽  
Characteristic Scales

Decaying vacuum cosmological models evolving smoothly between two extreme (very early and late time) de Sitter phases are able to solve or at least to alleviate some cosmological puzzles; among them we have (i) the singularity, (ii) horizon, (iii) graceful-exit from inflation, and (iv) the baryogenesis problem. Our basic aim here is to discuss how the coincidence problem based on a large class of running vacuum cosmologies evolving from de Sitter to de Sitter can also be mollified. It is also argued that even the cosmological constant problem becomes less severe provided that the characteristic scales of the two limiting de Sitter manifolds are predicted from first principles.

scholarly journals Toward Solving the Cosmological Constant Problem?

2003 ◽  
Vol 18 (18) ◽  
pp. 3221-3262 ◽  
Author(s):  
Olindo Corradini ◽  
Alberto Iglesias ◽  
Zurab Kakushadze
Keyword(s):  
Cosmological Constant ◽  
Extra Dimensions ◽  
Brane World ◽  
Infinite Volume ◽  
Brane Tension ◽  
Smooth Solutions ◽  
Cosmological Constant Problem ◽  
World Volume

We discuss the cosmological constant problem in the context of higher codimension brane world scenarios with infinite-volume extra dimensions. In particular, by adding higher curvature terms in the bulk action we are able to find smooth solutions with the property that the four-dimensional part of the brane world-volume is flat for a range of positive values of the brane tension.

scholarly journals Diluting Solutions of the Cosmological Constant Problem

2003 ◽  
Vol 18 (20) ◽  
pp. 1343-1353 ◽  
Author(s):  
Olindo Corradini ◽  
Alberto Iglesias ◽  
Zurab Kakushadze
Keyword(s):  
Cosmological Constant ◽  
Extra Dimensions ◽  
Brane World ◽  
Infinite Volume ◽  
Cosmological Constant Problem

We discuss the cosmological constant problem in the context of higher codimension brane world scenarios with infinite-volume extra dimensions.

scholarly journals Bootstrapped Newtonian Cosmology and the Cosmological Constant Problem

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 358
Author(s):  
Roberto Casadio ◽  
Andrea Giusti
Keyword(s):  
Black Holes ◽  
Cosmological Constant ◽  
Quantum Cosmology ◽  
Quantum Physics ◽  
Gravitational Interaction ◽  
Newtonian Gravity ◽  
Cosmological Constant Problem ◽  
Newtonian Cosmology ◽  
Natural Solution ◽  
The Impact

Bootstrapped Newtonian gravity was developed with the purpose of estimating the impact of quantum physics in the nonlinear regime of the gravitational interaction, akin to corpuscular models of black holes and inflation. In this work, we set the ground for extending the bootstrapped Newtonian picture to cosmological spaces. We further discuss how such models of quantum cosmology can lead to a natural solution to the cosmological constant problem.

The possibility of a stable flat dark energy-dominated Swiss-cheese brane-world universe

2020 ◽  
Vol 17 (05) ◽  
pp. 2050075
Author(s):  
Nasr Ahmed ◽  
Kazuharu Bamba ◽  
F. Salama
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Cosmological Models ◽  
Brane World ◽  
Fine Tuning ◽  
Energy Conditions ◽  
Late Time ◽  
Swiss Cheese ◽  
Black Strings ◽  
The Stability

In this paper, we study the possibility of obtaining a stable flat dark energy-dominated universe in a good agreement with observations in the framework of Swiss-cheese brane-world cosmology. Two different brane-world cosmologies with black strings have been introduced for any cosmological constant [Formula: see text] using two empirical forms of the scale factor. In both models, we have performed a fine-tuning between the brane tension and the cosmological constant so that the Equation of state (EoS) parameter [Formula: see text] for the current epoch, where the redshift [Formula: see text]. We then used these fine–tuned values to calculate and plot all parameters and energy conditions. The deceleration–acceleration cosmic transition is allowed in both models, and the jerk parameter [Formula: see text] at late-times. Both solutions predict a future dark energy-dominated universe in which [Formula: see text] with no crossing to the phantom divide line. While the pressure in the first solution is always negative, the second solution predicts a better behavior of cosmic pressure where the pressure is negative only in the late-time accelerating era but positive in the early-time decelerating era. Such a positive-to-negative transition in the evolution of pressure helps to explain the cosmic deceleration–acceleration transition. Since black strings have been proved to be unstable by some authors, this instability can actually reflect doubts on the stability of cosmological models with black strings (Swiss-cheese type brane-worlds cosmological models). For this reason, we have carefully investigated the stability through energy conditions and sound speed. Because of the presence of quadratic energy terms in Swiss-cheese type brane-world cosmology, we have tested the new nonlinear energy conditions in addition to the classical energy conditions. We have also found that a negative tension brane is not allowed in both models of the current work as the energy density will no longer be well defined.

scholarly journals TIME, VACUUM ENERGY, AND THE COSMOLOGICAL CONSTANT

2009 ◽  
Vol 18 (14) ◽  
pp. 2265-2268 ◽  
Author(s):  
VIQAR HUSAIN
Keyword(s):  
Quantum Gravity ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Cosmological Constant Problem ◽  
Problem Of Time ◽  
The Relationship

We describe a link between the cosmological constant problem and the problem of time in quantum gravity. This arises from examining the relationship between the cosmological constant and vacuum energy in light of nonperturbative formulations of quantum gravity.

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