EFFECTIVE COSMOLOGICAL CONSTANT IN BRANE COSMOLOGY

2006 ◽  
Vol 15 (06) ◽  
pp. 895-903
Author(s):  
SEN HU ◽  
JING-RONG WANG
Keyword(s):  
Cosmological Constant ◽  
Vacuum Energy ◽  
Brane World ◽  
Reflection Symmetry ◽  
Brane Cosmology ◽  
Effective Cosmological Constant ◽  
Dimensional Gravity ◽  
Bulk Cosmological Constant ◽  
Dimension One

We consider a brane-world of co-dimension one without reflection symmetry. Through it, we give a possible explanation of the great discrepancy between the vacuum energy and the observed cosmological constant without contradiction to the knowledge we have about our Universe. We also show the gravity observed will be standard four-dimensional gravity as long as the discrepancy of the bulk cosmological constant at different sides of the brane is small enough.

scholarly journals VACUUM ENERGY DENSITY AND COSMOLOGICAL CONSTANT IN dS BRANE-WORLD

2005 ◽  
Vol 20 (10) ◽  
pp. 2157-2168
Author(s):  
ZHE CHANG ◽  
SHAO-XIA CHEN ◽  
HAI-BAO WEN ◽  
XIN-BING HUANG
Keyword(s):  
Energy Density ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Brane World ◽  
Vacuum Energy Density ◽  
Massive Scalar Field ◽  
Bulk Cosmological Constant ◽  
Discrete Mass ◽  
The Relationship ◽  
Explicit Relation

We discuss the vacuum energy density and the cosmological constant of dS5 brane-world with a dilaton field. It is shown that a stable AdS4 brane can be constructed and gravity localization can be realized. An explicit relation between the dS bulk cosmological constant and the brane cosmological constant is obtained. The discrete mass spectrum of the massive scalar field in the AdS4 brane is used to acquire the relationship between the brane cosmological constant and the vacuum energy density. The vacuum energy density in the brane gotten by this method is in agreement with astronomical observations.

scholarly journals THE NATURE OF THE COSMOLOGICAL CONSTANT PROBLEM

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1545-1548 ◽  
Author(s):  
M. D. MAIA ◽  
A. J. S. CAPISTRANO ◽  
E. M. MONTE
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Energy Density ◽  
Cosmological Constant ◽  
Ground State ◽  
Vacuum Energy ◽  
Dimensional Space ◽  
Brane World ◽  
Vacuum Energy Density ◽  
Cosmological Constant Problem

General relativity postulates the Minkowski space-time as the standard (flat) geometry against which we compare all curved space-times and also as the gravitational ground state where particles, quantum fields and their vacua are defined. On the other hand, experimental evidences tell that there exists a non-zero cosmological constant, which implies in a deSitter ground state, which not compatible with the assumed Minkowski structure. Such inconsistency is an evidence of the missing standard of curvature in Riemann's geometry, which in general relativity manifests itself in the form of the cosmological constant problem. We show how the lack of a curvature standard in Riemann's geometry can be fixed by Nash's theorem on metric perturbations. The resulting higher dimensional gravitational theory is more general than general relativity, similar to brane-world gravity, but where the propagation of the gravitational field along the extra dimensions is a mathematical necessity, rather than a postulate. After a brief introduction to Nash's theorem, we show that the vacuum energy density must remain confined to four-dimensional space-times, but the cosmological constant resulting from the contracted Bianchi identity represents a gravitational term which is not confined. In this case, the comparison between the vacuum energy and the cosmological constant in general relativity does not make sense. Instead, the geometrical fix provided by Nash's theorem suggests that the vacuum energy density contributes to the perturbations of the gravitational field.

scholarly journals INFLATION INDUCED BY VACUUM ENERGY AND GRACEFUL EXIT FROM IT

2001 ◽  
Vol 16 (40) ◽  
pp. 2545-2555 ◽  
Author(s):  
E. PAPANTONOPOULOS ◽  
I. PAPPA
Keyword(s):  
Cosmological Constant ◽  
Vacuum Energy ◽  
Einstein Equations ◽  
Time Dependent ◽  
Brane Cosmology ◽  
Fast Growing ◽  
Early Epoch ◽  
The Universe ◽  
Natural Way

Motivated by brane cosmology, we solve the Einstein equations with a time-dependent cosmological constant. Assuming that at an early epoch the vacuum energy scales as 1/log t, we show that the universe passes from a fast growing phase (inflation) to an expanding phase in a natural way.

On the cosmological constant problem and brane-world geometry

Open Physics ◽  
2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Abraão Capistrano ◽  
Pedro Odon
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Energy Density ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Extrinsic Curvature ◽  
Brane World ◽  
Vacuum Energy Density ◽  
Cosmological Constant Problem ◽  
Riemannian Geometries

AbstractThe cosmological constant problem is examined within the context of the covariant brane-world gravity, based on Nash’s embedding theorem for Riemannian geometries. We show that the vacuum structure of the brane-world is more complex than General Relativity’s because it involves extrinsic elements, in specific, the extrinsic curvature. In other words, the shape (or local curvature) of an object becomes a relative concept, instead of the “absolute shape” of General Relativity. We point out that the immediate consequence is that the cosmological constant and the energy density of the vacuum quantum fluctuations have different physical meanings: while the vacuum energy density remains confined to the four-dimensional brane-world, the cosmological constant is a property of the bulk’s gravitational field that leads to the conclusion that these quantities cannot be compared, as it is usually done in General Relativity. Instead, the vacuum energy density contributes to the extrinsic curvature, which in turn generates Nash’s perturbation of the gravitational field. On the other hand, the cosmological constant problem ceases to be in the brane-world geometry, reappearing only in the limit where the extrinsic curvature vanishes.

scholarly journals LOCALIZING GRAVITY ON A 3-BRANE IN HIGHER DIMENSIONS

2001 ◽  
Vol 16 (supp01c) ◽  
pp. 943-945 ◽  
Author(s):  
TONY GHERGHETTA
Keyword(s):  
Magnetic Field ◽  
Cosmological Constant ◽  
Power Law ◽  
Higher Dimensions ◽  
Positive Zero ◽  
Dimensional Gravity ◽  
Bulk Cosmological Constant

We present metric solutions in six and higher dimensions with bulk cosmological constant, where gravity is localized on a 3-brane. The corrections to four-dimensional gravity from the bulk continuum modes are power-law suppressed. Furthermore, the introduction of a bulk "hedgehog" magnetic field leads to a regular geometry, and can localize gravity on the 3-brane with either positive, zero or negative bulk cosmological constant.

EFFECTIVE 3-BRANE BRANS–DICKE COSMOLOGY

2008 ◽  
Vol 23 (06) ◽  
pp. 401-415 ◽  
Author(s):  
AHMAD RAMI EL-NABULSI
Keyword(s):  
Cosmological Constant ◽  
Scalar Fields ◽  
Brane Cosmology ◽  
High Energies ◽  
Effective Cosmological Constant ◽  
String Theories

A Brans–Dicke brane cosmology with two scalar fields inspired from string theories and phenomenological effective cosmological constant is investigated and some features are described in some details, in particular the low and high energies limit.

BRANE SOLUTIONS WITH A QUADRATIC POTENTIAL IN STRING FRAME

2006 ◽  
Vol 21 (28n29) ◽  
pp. 5823-5831
Author(s):  
JAE-HYUK OH ◽  
YONGSUNG YOON
Keyword(s):  
Cosmological Constant ◽  
Flat Space ◽  
Brane World ◽  
Low Energy ◽  
Quadratic Potential ◽  
Brane Solution ◽  
Bulk Cosmological Constant ◽  
Potential Parameters ◽  
String Gravity ◽  
Bulk Space

We have examined brane world solutions for the low energy effective string gravity action coupled with a quadratic dilaton potential in string frame. For a negative bulk cosmological constant, static 3-brane solutions exist. Their properties are analyzed depending on the quadratic potential parameters. It is found that a brane solution in a curved bulk space in Einstein frame corresponds to a dilaton solution in flat space in string frame.

MIRROR BRANES

2005 ◽  
Vol 20 (30) ◽  
pp. 2283-2294 ◽  
Author(s):  
YURI SHTANOV ◽  
ALEXANDER VIZNYUK
Keyword(s):  
Cosmological Constant ◽  
Scalar Curvature ◽  
Vacuum Energy ◽  
Vacuum Solution ◽  
Matter Content ◽  
Brane Model ◽  
Gravitational Forces ◽  
Dimensional Gravity ◽  
The One ◽  
Reasonable Model

The Randall–Sundrum two-brane model admits the flat-brane Lorentz-invariant vacuum solution only if the branes have exactly opposite tensions. We pay attention to this condition and propose a generalization of this model in which two branes are described by actions of the same form and with the same matter content but with opposite signs. In this way, the relation between their tensions (which are their vacuum energy densities) is naturally accounted for. We study a simple example of such a model in detail. It represents the Randall–Sundrum model supplemented by the Einstein scalar-curvature terms in the actions for the branes. We show that this model is tachyon-free for sufficiently large negative values of the brane cosmological constant, that gravitational forces on the branes are of opposite signs, and that physically most reasonable model of this type is the one where the five-dimensional gravity is localized around the visible brane. The massive gravitational modes in this model have ghost-like character, and we discuss the significance of this fact for the quantum instability of the vacuum on the visible brane.

scholarly journals CONSTRAINTS ON THE COSMOLOGICAL CONSTANT DUE TO SCALE INVARIANCE

2010 ◽  
Vol 25 (16) ◽  
pp. 1349-1364 ◽  
Author(s):  
PAVAN K. ALURI ◽  
PANKAJ JAIN ◽  
SUBHADIP MITRA ◽  
SUKANTA PANDA ◽  
NAVEEN K. SINGH
Keyword(s):  
Cosmological Constant ◽  
Scale Invariance ◽  
Vacuum Energy ◽  
Higgs Field ◽  
Gauge Fields ◽  
Simple Relationship ◽  
Massless Fermion ◽  
Fermion Fields ◽  
Effective Cosmological Constant ◽  
The Standard Model

We consider the standard model with local scale invariance. The theory shows exact scale invariance of dimensionally regulated action. We show that massless gauge fields, which may be Abelian or non-Abelian, lead to vanishing contribution to the cosmological constant in this theory. This result follows in the quantum theory, to all orders in the gauge couplings. However, we have not considered contributions higher orders in the gravitational coupling. Similarly we also find that massless fermion fields yield null contribution to the cosmological constant. The effective cosmological constant in this theory is nonzero due to the phenomenon of cosmological symmetry breaking, which also gives masses to all the massive fields, besides generating the Planck mass. We find a simple relationship between the curvature scalar and the vacuum value of the Higgs field in the limit when we ignore all other contributions to the energy density besides the vacuum energy.

GRAVITY AND COSMOLOGY ON A BRANE-WORLD

2002 ◽  
Vol 17 (20) ◽  
pp. 2651-2654
Author(s):  
RICHARD A. BATTYE
Keyword(s):  
Scalar Field ◽  
Einstein Gravity ◽  
Brane World ◽  
Reflection Symmetry ◽  
Everyday Experience ◽  
Spatial Dimensions ◽  
Dimension One

Contrary to everyday experience it is possible to construct models with more than three spatial dimensions which are compatible with linearized 4D Einstein gravity and homogeneous isotropic cosmologies. The simplest of these models have co-dimension one and are subjected to reflection symmetry. We discuss various extensions, in particular the inclusion of a scalar field and the relaxation of the assumption of reflection symmetry.

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