Brans-Dicke cosmology with time-dependent cosmological term

1990 ◽  
Vol 29 (12) ◽  
pp. 1419-1421 ◽  
Author(s):  
Marcelo Samuel Berman
Keyword(s):  
Cosmological Term ◽  
Time Dependent

Brans-Dicke models with time-dependent cosmological term

1990 ◽  
Vol 29 (12) ◽  
pp. 1411-1414 ◽  
Author(s):  
Marcelo Samuel Berman ◽  
M. M. Som
Keyword(s):  
Cosmological Term ◽  
Time Dependent

Nonsingular cosmology with a time-dependent cosmological term

1994 ◽  
Vol 50 (12) ◽  
pp. 7725-7728 ◽  
Author(s):  
Arbab I. Arbab ◽  
A-M. M. Abdel-Rahman
Keyword(s):  
Cosmological Term ◽  
Time Dependent

scholarly journals The Recombination in a FRW Universe with a Variable Cosmological Term

2000 ◽  
Vol 198 ◽  
pp. 118-119
Author(s):  
N. Pires ◽  
J. A. S. Lima
Keyword(s):  
Large Scale ◽  
Cosmological Term ◽  
Time Dependent ◽  
Physical Processes ◽  
Frw Universe ◽  
Variable Cosmological Term ◽  
Primordial Plasma ◽  
Density Perturbations ◽  
The Universe ◽  
Recombination Epoch

The effects of a time-dependent A term in the recombination epoch are analysed taking into account the main physical processes occurring in the primordial plasma. For a vacuum decaying into photons, we show that the recombination begins when the Universe was smaller and denser, leading to a greater recombination rate. These results may have several implications to the large scale structure. In particular, the earlier recombination means that more time is available to the evolution of density perturbations.

The Large Numbers Hypothesis and a Relativistic Theory of Gravitation

1986 ◽  
Vol 39 (3) ◽  
pp. 339 ◽  
Author(s):  
YK Lau ◽  
SJ Prokhovnik
Keyword(s):  
Scalar Field ◽  
Scalar Potential ◽  
Cosmological Term ◽  
Time Dependent ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Tensor Theory ◽  
Large Numbers ◽  
Dependent Form ◽  
Theory Of Gravitation

A way to reconcile Dirac's large numbers hypothesis and Einstein's theory of gravitation wasrecently suggested by Lau (1985). It is characterized by the conjecture of a time-dependentcosmological term and gravitational term in Einstein's field equations. Motivated by thisconjecture and the large numbers hypothesis, we formulate here a scalar-tensor theory in terms of an action principle. The cosmological term is required to be spatially dependent as well as time dependent in general. The theory developed is applied to a cosmological model compatible with the large numbers' hypothesis. The time-dependent form of the cosmological term and the scalar potential are then deduced. A possible explanation of the smallness of the cosmological term is also given and the possible significance of the scalar field is speculated.

SOLVING THE "WHY NOW?" PUZZLE

2005 ◽  
Vol 20 (27) ◽  
pp. 6200-6210
Author(s):  
MAQBOOL AHMED
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Set Theory ◽  
Constant Term ◽  
Cosmological Term ◽  
Fundamental Question ◽  
Time Dependent ◽  
History Of ◽  
The Right ◽  
The Universe

A variety of observations indicate that the universe is dominated by dark energy with negative pressure, one possibility for which is a cosmological constant. If the dark energy is a cosmological constant, a fundamental question is: Why has it become relevant at so late an epoch, making today the only time in the history of the universe at which the cosmological constant is of order the ambient density. Ideas from Causal Set theory and Unimodular Gravity provide an answer, leading to a time dependent cosmological "constant" term of the right magnitude. I will briefly review the motivation behind the model, the ansatz that yields this fluctuating cosmological term, which is always of order the ambient density and summarize the results of the computer simulations based on the model.

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