scholarly journals Exact cosmological solution of a scalar-tensor gravity theory compatible with theΛCDMmodel

2011 ◽  
Vol 83 (4) ◽  
Author(s):  
B. Boisseau
Keyword(s):  
Cosmological Solution ◽  
Gravity Theory ◽  
Exact Cosmological Solution

Inflationary cosmological universe containing dark matter and many charged galaxies

1988 ◽  
Vol 66 (11) ◽  
pp. 1031-1034
Author(s):  
A Das ◽  
Daniel Kay
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Time Evolution ◽  
Electromagnetic Fields ◽  
Cosmological Solution ◽  
Charged Matter ◽  
Charged Black Holes ◽  
The Third ◽  
Exact Cosmological Solution ◽  
The Universe

Within the framework of Einstein's theory, cosmological universes are considered that contain three types of "fluids." A neutral cosmological fluid (dark matter), which is present everywhere, determines the overall time evolution of the universe. The second type consists of charged matter that constitutes the cores of galaxies. The electromagnetic fields generated by the charged matter make up the third kind of fluid, which is evidently null. An exact cosmological solution is furnished that provides for an early inflationary period and contains many charged black holes as galactic cores.

scholarly journals Cosmological Bounce and Some Other Solutions in Exponential Gravity

Universe ◽  
2018 ◽  
Vol 4 (10) ◽  
pp. 105 ◽  
Author(s):  
Pritha Bari ◽  
Kaushik Bhattacharya ◽  
Saikat Chakraborty
Keyword(s):  
Cosmological Constant ◽  
Cosmological Solution ◽  
Constant Term ◽  
Gravity Theory ◽  
De Sitter ◽  
Sitter Solution ◽  
Higher Derivative ◽  
New Type ◽  
Theories Of Gravity ◽  
Theory Of Gravity

In this work, we present some cosmologically relevant solutions using the spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime in metric f ( R ) gravity where the form of the gravitational Lagrangian is given by 1 α e α R . In the low curvature limit this theory reduces to ordinary Einstein-Hilbert Lagrangian together with a cosmological constant term. Precisely because of this cosmological constant term this theory of gravity is able to support nonsingular bouncing solutions in both matter and vacuum background. Since for this theory of gravity f ′ and f ″ is always positive, this is free of both ghost instability and tachyonic instability. Moreover, because of the existence of the cosmological constant term, this gravity theory also admits a de-Sitter solution. Lastly we hint towards the possibility of a new type of cosmological solution that is possible only in higher derivative theories of gravity like this one.

scholarly journals ELKO SPINOR MODEL WITH TORSION AND COSMOLOGY

2013 ◽  
Vol 28 (29) ◽  
pp. 1350121 ◽  
Author(s):  
SEYEN KOUWN ◽  
JOOHAN LEE ◽  
TAE HOON LEE ◽  
PHILLIAL OH
Keyword(s):  
Torsion Tensor ◽  
Cosmological Solution ◽  
Fine Tuning ◽  
Dirac Spinor ◽  
Minimal Coupling ◽  
Coincidence Problem ◽  
Time Component ◽  
Spinor Model ◽  
Exact Cosmological Solution ◽  
The Universe

We investigate the cosmology of ELKO spinor model when minimal coupling with torsion is included. Unlike the Dirac spinor which interacts only with the totally anti-symmetric components of torsion tensor, we find the interaction of the time component of the trace of torsion tensor with ELKO spinor provides different aspects of cosmology with fermions. We discuss a couple of cases with given potentials of ELKO spinor which can result in interesting cosmological consequences. Especially, we show that there exists an exact cosmological solution in which the universe began its acceleration only recently and this solution is an attractor. This corresponds to specific forms of torsion and potential with a mild fine-tuning which can address the coincidence problem.

An oscillatory big-bang singularity

1986 ◽  
Vol 64 (2) ◽  
pp. 200-203 ◽  
Author(s):  
J. Wainwright
Keyword(s):  
Cosmological Solution ◽  
Big Bang ◽  
Clock Time ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Cosmological Solutions ◽  
Exact Cosmological Solution ◽  
Self Similar ◽  
The Big Bang ◽  
Big Bang Singularity

The big-bang singularities in the exact cosmological solutions of the Einstein field equations that have been studied up to now are power asymptotes in the sense that all scalar polynomials in the curvature tensor diverge monotonically as a power of clock time along the fundamental world lines, as the singularity is approached. One can thus regard the solutions as being asymptotically self-similar near the singularity. In this paper, we illustrate a more complicated type of singularity by giving an example of an exact cosmological solution in which the big-bang singularity is of an oscillatory nature, so that the solution is not asymptotically self-similar.

AN EXACT COSMOLOGICAL SOLUTION WITH ENERGY EXCHANGE BETWEEN VACUUM AND MATTER, AND VACUUM AND RADIATION

2008 ◽  
Vol 23 (13) ◽  
pp. 971-977 ◽  
Author(s):  
GUANG-WEN MA ◽  
JING-YUAN MA
Keyword(s):  
Energy Exchange ◽  
Cosmological Solution ◽  
Two Fluids ◽  
Walker Metric ◽  
Exact Cosmological Solution

We extend the cosmological version with energy exchange proposed by Barrow and Clifton from the case of two fluids to the case of three fluids, and find an exact cosmological solution for spatially flat Robertson–Walker metric. In this solution the integrating constants and the parameters introduced by the model are determined from cosmic observations.

A Gravity Theory on Noncommutative Spaces

2007 ◽  
Author(s):  
Frank Meyer ◽  
P. Aschieri ◽  
C. Blohmann ◽  
M. Dimitrijevic ◽  
P. Schupp ◽  
...  
Keyword(s):  
Gravity Theory ◽  
Noncommutative Spaces
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