Viscous cosmological models with a variable cosmological term

2004 ◽  
Vol 9 (4) ◽  
Author(s):  
Z.T. Nkosi
Author(s):  
Archana Dixit ◽  
Anirudh Pradhan ◽  
Dinesh Chandra Maurya

In this paper, we have investigated the physical behavior of cosmological models in modified Teleparallel gravity with a general function [Formula: see text] where [Formula: see text] and [Formula: see text] are model parameters and [Formula: see text] is the torsion scalar. We have considered a homogeneous and isotropic Friedman universe filled with perfect fluid. We have derived the deceleration parameter [Formula: see text] in terms of equation of state (EoS) parameter [Formula: see text] and Hubble parameter [Formula: see text]. We have investigated the variation of [Formula: see text] over the observed values of Hubble constant in various observations within the range of redshift [Formula: see text]. Also, we have studied effective energy density [Formula: see text], effective pressure [Formula: see text] and effective EoS parameter [Formula: see text]. We have observed that the second term of [Formula: see text] function behaves just like variable cosmological term [Formula: see text] ([Formula: see text]) at late-time universe and causes the acceleration in expansion and works just like dark energy candidates. Also, we have evaluated the age of the present universe for various stages of matter [Formula: see text] and various [Formula: see text] functions.


2000 ◽  
Vol 15 (05) ◽  
pp. 333-342
Author(s):  
L. O. PIMENTEL ◽  
CESAR MORA

We consider quantum cosmology for some scalar–tensor theories of gravitation in the case of homogeneous and isotropic cosmological models. We present quantum solutions corresponding to cosmological term: (i) λ(ϕ) = 0 and (ii) λ(ϕ) = 3qϕ. In the first case we find a solution that can be interpreted as a quantum wormhole since it satisfies the Hawking–Page regularity conditions. Also, we obtain the WKB approximation.


2003 ◽  
Vol 20 (16) ◽  
pp. 3797-3814 ◽  
Author(s):  
K A Bronnikov ◽  
A Dobosz ◽  
I G Dymnikova

2015 ◽  
Vol 70 (11) ◽  
pp. 905-911 ◽  
Author(s):  
Carlos Blanco-Pérez ◽  
Antonio Fernández-Guerrero

AbstractWe propose a model of expansion of the universe in which a minimal, ‘quantised’ rate is dependent upon the value of the cosmological constant Λ in Einstein’s field equations, itself not a constant but a function of the size and the entropy of the universe. From this perspective, we offer an expression which relates Hubble’s constant with the cosmological constant.


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