scholarly journals A VARYING-e BRANE WORLD COSMOLOGY

2002 ◽  
Vol 17 (03) ◽  
pp. 175-184 ◽  
Author(s):  
DONAM YOUM
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Electric Charge ◽  
Brane World ◽  
Speed Of Light ◽  
Cosmological Constant Problem ◽  
System Of Units ◽  
Flatness Problem

We study a varying electric charge brane world cosmology in the RS2 model obtained from a varying-speed-of-light brane world cosmology by redefining the system of units. We elaborate conditions under which the flatness problem and the cosmological constant problem can be resolved by such cosmological model.

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.

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 A Unified Cosmological Model for Solution of Problems of Cosmological Constant, Cosmic Coincidence, Energy Conservation, Flatness and Homogeneity of Horizon

2021 ◽  
Author(s):  
Biswaranjan Dikshit
Keyword(s):  
Energy Density ◽  
Cosmological Model ◽  
Energy Conservation ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
Zero Energy ◽  
Cosmological Constant Problem ◽  
Coincidence Problem ◽  
Horizon Problem

Cosmological constant problem is the difference by a factor of ~10123 between quantum mechanically calculated vacuum energy density and astronomically observed value. Cosmic coincidence problem questions why matter energy density is of the same order as the present vacuum energy density (former is ~32% and latter is ~68%). Recently, by quantizing zero-point field of space, we have developed a cosmological model that predicts correct value of vacuum and non-vacuum energy density. In this paper, we remove some earlier assumptions and develop a generalized version of our cosmological model to solve three more problems viz. energy conservation, flatness and horizon problem along with the above two. For creation of universe without violating law of energy conservation, net energy of the universe including (negative) gravitational potential energy must be zero. However, in conventional method, its quantitative proof needs the space to be exactly flat i.e. zero-energy universe is a consequence of flatness. But, in this paper, we will prove a zero-energy universe without using flatness of space and then show that flatness is actually a consequence of zero energy density. Finally, using our model we solve the horizon problem of universe. Although cosmic inflation can explain the flatness of space and uniformity of horizon by invoking inflaton field, it cannot predict the present value of vacuum energy density or matter density. But, our cosmological model solves in an unified manner all the above mentioned five problems viz. cosmological constant problem, cosmic coincidence problem, energy conservation, flatness and horizon problem.

scholarly journals The cosmological constant problem from a brane-world perspective

2000 ◽  
Vol 2000 (09) ◽  
pp. 034-034 ◽  
Author(s):  
Stefan Förste ◽  
Zygmunt Lalak ◽  
Stéphane Lavignac ◽  
Hans Peter Nilles
Keyword(s):  
Cosmological Constant ◽  
Brane World ◽  
Cosmological Constant Problem ◽  
World Perspective

scholarly journals Brane World Solution to the Cosmological Constant Problem

2001 ◽  
Vol 86 (9) ◽  
pp. 1682-1685 ◽  
Author(s):  
S.-H. Henry Tye ◽  
Ira Wasserman
Keyword(s):  
Cosmological Constant ◽  
Brane World ◽  
Cosmological Constant Problem

scholarly journals SOLUTIONS TO COSMOLOGICAL PROBLEMS WITH ENERGY CONSERVATION AND VARYING c, G AND Λ

2001 ◽  
Vol 16 (15) ◽  
pp. 957-961 ◽  
Author(s):  
P. GOPAKUMAR ◽  
G. V. VIJAYAGOVINDAN
Keyword(s):  
Energy Conservation ◽  
Cosmological Constant ◽  
Coupling Strength ◽  
Cosmological Parameter ◽  
Gravitational Coupling ◽  
Speed Of Light ◽  
Present Solution ◽  
Previous Solution ◽  
Flatness Problem

The flatness and cosmological constant problems are solved with varying speed of light c, gravitational coupling strength G and cosmological parameter Λ, by explicitly assuming energy conservation of observed matter. The present solution to the flatness problem is the same as a previous solution in which energy conservation was absent.

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