Time dependent G and Λ cosmological model in f(R,T) gravity

New Astronomy ◽  
2021 ◽  
pp. 101760
Author(s):  
Leishingam Kumrah ◽  
S. Surendra Singh ◽  
Lambamayum Anjana Devi
Keyword(s):  
Cosmological Model ◽  
Time Dependent

scholarly journals The Large Number Hypothesis and Einstein's Theory of Gravitation

1985 ◽  
Vol 38 (4) ◽  
pp. 547 ◽  
Author(s):  
Yun-Kau Lau
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Matter Density ◽  
Time Dependent ◽  
Field Equations ◽  
Large Number Hypothesis ◽  
Theory Of Gravitation ◽  
The Mean ◽  
Limiting Case ◽  
The Universe

In an attempt to reconcile the large number hypothesis (LNH) with Einstein's theory of gravitation, a tentative generalization of Einstein's field equations with time-dependent cosmological and gravitational constants is proposed. A cosmological model consistent with the LNH is deduced. The coupling formula of the cosmological constant with matter is found, and as a consequence, the time-dependent formulae of the cosmological constant and the mean matter density of the Universe at the present epoch are then found. Einstein's theory of gravitation, whether with a zero or nonzero cosmological constant, becomes a limiting case of the new generalized field equations after the early epoch.

scholarly journals A NEW COSMOLOGICAL CONSTANT MODEL

1996 ◽  
Vol 11 (01) ◽  
pp. 1-7 ◽  
Author(s):  
JORGE L. LOPEZ ◽  
D.V. NANOPOULOS
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Hubble Parameter ◽  
Particle Physics ◽  
Time Dependent ◽  
Low Density ◽  
Universe Model ◽  
Planck Time ◽  
Age Of The Universe ◽  
The Universe

We propose a new cosmological model with a time-dependent cosmological constant (Λ∝1/t2), which starting at the Planck time as [Formula: see text], evolves to the present-day allowed value of [Formula: see text]. This scenario is supported by noncritical string theory considerations. We compute the age of the Universe and the time dependence of the scale factor in this model, and find general agreement with recent determinations of the Hubble parameter for substantial values of ΩΛ. This effectively low-density open Universe model differs from the traditional cosmological constant model, and has observable implications for particle physics and cosmology.

scholarly journals ON TIME-DEPENDENT BLACK HOLES AND COSMOLOGICAL MODELS FROM A KALUZA–KLEIN MECHANISM

2009 ◽  
Vol 24 (07) ◽  
pp. 1383-1415
Author(s):  
C. CASTRO ◽  
J. A. NIETO ◽  
L. RUIZ ◽  
J. SILVAS
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmological Model ◽  
Black Hole Entropy ◽  
Time Dependent ◽  
Einstein Field Equations ◽  
Schwarzschild Black Hole ◽  
Field Equations ◽  
Newman Black Hole ◽  
Kaluza Klein

Novel static, time-dependent and spatial–temporal solutions to Einstein field equations, displaying singularities, with and without horizons, and in several dimensions, are found based on a dimensional reduction procedure widely used in Kaluza–Klein-type theories. The Kerr–Newman black hole entropy as well as the Reissner–Nordstrom, Kerr and Schwarzschild black hole entropy are derived from the corresponding Euclideanized actions. A very special cosmological model based on the dynamical interior geometry of a black hole is found that has no singularities at t = 0 due to the smoothing of the mass distribution. We conclude with another cosmological model equipped also with a dynamical horizon and which is related to Vaidya's metric (associated with the Hawking radiation of black holes) by interchanging t ↔ r, which might render our universe a dynamical black hole.

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