On the Removal of Initial Singularity in a Big-Bang Universe in Terms of a Renormalized Theory of Gravitation. II

We give a mathematically exact and physically faithful embedding of curved 4D cosmology in a flat 5D space, thereby enabling visualization of the big bang in a new and informative way. In fact, in unified theories of fields and particles with real extra dimensions, it is possible to dispense with the initial singularity.

Download Full-text

Big-Bang nucleosynthesis: Constraints on nuclear reaction rates, neutrino degeneracy, inhomogeneous and Brans–Dicke models

International Journal of Modern Physics E ◽

10.1142/s0218301317410038 ◽

2017 ◽

Vol 26 (08) ◽

pp. 1741003 ◽

Cited By ~ 12

Author(s):

Riou Nakamura ◽

Masa-Aki Hashimoto ◽

Ryotaro Ichimasa ◽

Kenzo Arai

Keyword(s):

Cosmological Constant ◽

Nuclear Reaction ◽

Recent Progress ◽

Reaction Rates ◽

Big Bang ◽

Big Bang Nucleosynthesis ◽

Friedmann Model ◽

Theory Of Gravitation ◽

The Big Bang

We review the recent progress in the Big-Bang nucleosynthesis which includes the standard and nonstandard theory of cosmology, effects of neutrino degeneracy, and inhomogeneous nucleosynthesis within the framework of a Friedmann model. As for a nonstandard theory of gravitation, we adopt a Brans–Dicke theory which incorporates a cosmological constant. We constrain various parameters associated with each subject.

Download Full-text

HIGHER DIMENSIONAL SZEKERES' SPACE–TIME IN BRANS–DICKE SCALAR TENSOR THEORY

International Journal of Modern Physics D ◽

10.1142/s0218271804005055 ◽

2004 ◽

Vol 13 (06) ◽

pp. 1073-1083

Author(s):

ASIT BANERJEE ◽

UJJAL DEBNATH ◽

SUBENOY CHAKRABORTY

Keyword(s):

Turning Point ◽

Coupling Parameter ◽

Big Bang ◽

Space Time ◽

Scalar Tensor Theory ◽

Field Equations ◽

Tensor Theory ◽

Higher Dimensional ◽

Theory Of Gravitation ◽

The Big Bang

The generalized Szekeres family of solution for quasi-spherical space–time of higher dimensions are obtained in the scalar tensor theory of gravitation. Brans–Dicke field equations expressed in Dicke's revised units are exhaustively solved for all the subfamilies of the said family. A particular group of solutions may also be interpreted as due to the presence of the so-called C-field of Hoyle and Narlikar and for a chosen sign of the coupling parameter. The models show either expansion from a big bang type of singularity or a collapse with the turning point at a lower bound. There is one particular case which starts from the big bang, reaches a maximum and collapses with the in course of time to a crunch.

Download Full-text

The early universe in a generalized theory of gravitation

Canadian Journal of Physics ◽

10.1139/p82-091 ◽

1982 ◽

Vol 60 (5) ◽

pp. 659-663 ◽

Cited By ~ 8

Author(s):

J. W. Moffat ◽

D. Vincent

Keyword(s):

Early Universe ◽

Initial Conditions ◽

Big Bang ◽

Field Equations ◽

Anisotropic Solution ◽

Plane Symmetric ◽

Frw Model ◽

Theory Of Gravitation ◽

The Big Bang ◽

The Universe

The standard Friedmann–Robertson–Walker (FRW) big-bang model of the universe requires special initial conditions: the early universe is highly homogeneous and isotropic even though there exist causally disconnected regions (horizon problem). A plane symmetric (anisotropic) solution of a system of field equations in a generalized theory of gravitation, predicts the beginning of the universe as a vacuum instability at a specific fundamental time (which can be associated with the Planck time (tp)), after which matter is created as the universe begins to expand. At a time t = tc there is a singular expansion, the anisotropy vanishes, and the physical horizon becomes infinite. Thereafter the solution of the field equations goes over into the FRW model. Thus the special initial conditions of the FRW model at the big-bang singularity t = tc are predicted by the theory.

Download Full-text

Anisotropic MHRDE model in BD theory of gravitation

International Journal of Geometric Methods in Modern Physics ◽

10.1142/s0219887819501858 ◽

2019 ◽

Vol 16 (12) ◽

pp. 1950185

Author(s):

Anirudh Pradhan ◽

Archana Dixit ◽

Shilpi Singhal

Keyword(s):

Dark Energy ◽

Energy Density ◽

Deceleration Parameter ◽

Big Bang ◽

Smooth Transition ◽

Complete Agreement ◽

Symmetric Model ◽

Axially Symmetric ◽

Theory Of Gravitation ◽

The Universe

In this paper, in the framework of the Brans–Dicke [Phys. Rev. 124 (1961) 925] Gravitation theory, we propose to study the spatially homogeneous, anisotropic and axially symmetric model filled with dark matter and dark energy. Here, we consider the modified holographic Ricci dark energy proposed by Chen and Jing [Phys. Rev. B 679 (2009) 144] as a feasible state of darkness. To achieve a solution, we consider the time-dependent deceleration parameter, which contributes to the average scale factor of [Formula: see text], where [Formula: see text] and [Formula: see text] are arbitrary constants. We have derived field equations of Brans–Dicke theory of gravitation with the help of an axially symmetric anisotropic Bianchi-type space-time. We have determined the cosmological parameters, namely, deceleration parameter, matter energy density, anisotropic dark energy density, BD scalar field, skewness parameter, EoS parameter and jerk parameter. Here, the various phenomena like the Big Bang, expanding the universe, and shift from anisotropy to isotropy are observed in the model. A comprehensive physical debate of these dynamic parameters is provided through a graphical representation. We observe that we have a quintessence model that exhibits a smooth transition from decelerated stage to an accelerated phase of the universe. This situation is in complete agreement with the modern cosmology scenario. Some physical and geometric behaviors are also discussed and discovered to be in excellent agreement with SNe Ia Supernova’s latest observations.

Download Full-text

A holographic big bang?

International Journal of Modern Physics D ◽

10.1142/s0218271815440290 ◽

2015 ◽

Vol 24 (12) ◽

pp. 1544029

Author(s):

N. Afshordi ◽

R. B. Mann ◽

R. Pourhasan

Keyword(s):

Cosmological Model ◽

Big Bang ◽

Initial Singularity ◽

Scale Invariant ◽

The Big Bang ◽

The Universe ◽

Important Test

We present a cosmological model in which the Universe emerges out of the collapse of a five-dimensional (5D) star as a spherical three-brane. The initial singularity of the big bang becomes hidden behind a causal horizon. Near scale-invariant primordial curvature perturbations can be induced on the brane via a thermal atmosphere that is in equilibrium with the brane, circumventing the need for a separate inflationary process and providing an important test of the model.

Download Full-text

A FLAT SPACETIME MODEL OF THE UNIVERSE

Modern Physics Letters A ◽

10.1142/s021773231250201x ◽

2012 ◽

Vol 27 (36) ◽

pp. 1250201 ◽

Cited By ~ 15

Author(s):

PANKAJ JAIN

Keyword(s):

Energy Density ◽

Big Bang ◽

Initial Singularity ◽

Radiative Energy ◽

Flat Spacetime ◽

Spacetime Metric ◽

Radiative Temperature ◽

Big Bang Model ◽

The Masses ◽

The Universe

We propose a model of the Universe based on Minkowski flat spacetime metric. In this model the spacetime does not evolve. Instead the matter evolves such that all the mass parameters increase with time. We construct a model based on unimodular gravity to show how this can be accomplished within the framework of flat spacetime. We show that the model predicts the Hubble law if the masses increase with time. Furthermore, we show that it fits the high z supernova data in a manner almost identical to the standard Big Bang model. Furthermore, we show that at early times the Universe is dominated by radiative energy density. The phenomenon of recombination also arises in our model and hence predicts the existence of CMBR. However, a major difference with respect to the standard Big Bang is that there is no initial singularity and the radiative temperature and energy density do not evolve in our model. Furthermore, we argue that the basic motivation for inflation is absent in our model.

Download Full-text

A Note on Singularity Avoidance in Fourth-Order Gravity

Universe ◽

10.3390/universe8010051 ◽

2022 ◽

Vol 8 (1) ◽

pp. 51

Author(s):

Luca Fabbri

Keyword(s):

Black Holes ◽

Fourth Order ◽

Short Distance ◽

Big Bang ◽

Singularity Avoidance ◽

Theory Of Gravitation ◽

The Big Bang ◽

General Perspective

We consider the fourth-order differential theory of gravitation to treat the problem of singularity avoidance: studying the short-distance behaviour in the case of black-holes and the big-bang we are going to see a way to attack the issue from a general perspective.

Download Full-text

Nonsingular Einsteinian Cosmology: How Galactic Momentum Prevents Cosmic Singularities

Journal of Gravity ◽

10.1155/2013/617142 ◽

2013 ◽

Vol 2013 ◽

pp. 1-3

Author(s):

Kenneth J. Epstein

Keyword(s):

Vacuum Energy ◽

Big Bang ◽

Negative Energy ◽

Initial Singularity ◽

Accelerated Expansion ◽

Positive Energy ◽

Spatial Expansion ◽

Expanding Universe ◽

Galactic Clusters ◽

Classical Effect

It is shown how Einstein's equation can account for the evolution of the universe without an initial singularity and can explain the inflation epoch as a momentum dominated era in which energy from matter and radiation drove extremely accelerated expansion of space. It is shown how an object with momentum loses energy to the expanding universe and how this energy can contribute to accelerated spatial expansion more effectively than vacuum energy, because virtual particles, the source of vacuum energy, can have negative energy, which can cancel any positive energy from the vacuum. Radiation and matter with momentum have positive but decreasing energy in the expanding universe, and the energy lost by them can contribute to accelerated spatial expansion between galactic clusters, making dark energy a classical effect that can be explained by general relativity without quantum mechanics, and, as (13) and (15) show, without an initial singularity or a big bang. This role of momentum, which was overlooked in the Standard Cosmological Model, is the basis of a simpler model which agrees with what is correct in the old model and corrects what is wrong with it.

Download Full-text