The cosmological term, compensation and singularities

1974 ◽  
Vol 17 (12) ◽  
pp. 1661-1666
Author(s):  
D. D. Ivanenko
Keyword(s):  
Cosmological Term

ON A PERFECT FLUID K¨ AHLER SPACETIME

2016 ◽  
Vol 12 (3) ◽  
pp. 4350-4355
Author(s):  
VIBHA SRIVASTAVA ◽  
P. N. PANDEY
Keyword(s):  
Field Equation ◽  
Perfect Fluid ◽  
Sectional Curvature ◽  
Einstein Field Equation ◽  
Cosmological Term ◽  
Conformal Killing ◽  
Killing Vectors ◽  
Projectively Flat ◽  
Conformal Killing Vectors

The object of the present paper is to study a perfect fluid K¨ahlerspacetime. A perfect fluid K¨ahler spacetime satisfying the Einstein field equation with a cosmological term has been studied and the existence of killingand conformal killing vectors have been discussed. Certain results related to sectional curvature for pseudo projectively flat perfect fluid K¨ahler spacetime have been obtained. Dust model for perfect fluid K¨ahler spacetime has also been studied.

Expanding models with a varying cosmological term and bulk stress

1996 ◽  
Vol 28 (6) ◽  
pp. 679-689 ◽  
Author(s):  
Vicenç Méndez ◽  
Diego Pavón
Keyword(s):  
Cosmological Term ◽  
Bulk Stress

scholarly journals Generalized supersymmetric cosmological term in N=1 supergravity

2015 ◽  
Vol 2015 (8) ◽  
Author(s):  
P. K. Concha ◽  
E. K. Rodríguez ◽  
P. Salgado
Keyword(s):  
Cosmological Term

scholarly journals Almost-Pseudo-Ricci Symmetric FRW Universe with a Dynamic Cosmological Term and Equation of State

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 205
Author(s):  
Sanjay Mandal ◽  
Avik De ◽  
Tee-How Loo ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
Cosmological Term ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Late Time ◽  
Frw Universe ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

On the Tolman-Bondi model with cosmological term

1991 ◽  
Vol 106 (4) ◽  
pp. 413-418 ◽  
Author(s):  
A. Zecca
Keyword(s):  
Cosmological Term

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

A probe of cosmological models in modified teleparallel gravity

2021 ◽  
pp. 2150208
Author(s):  
Archana Dixit ◽  
Anirudh Pradhan ◽  
Dinesh Chandra Maurya
Keyword(s):  
Hubble Constant ◽  
Teleparallel Gravity ◽  
Cosmological Term ◽  
Cosmological Models ◽  
Model Parameters ◽  
Late Time ◽  
General Function ◽  
Eos Parameter ◽  
Variable Cosmological Term ◽  
Present Universe

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.

scholarly journals Cosmological constant, matter, cosmic inflation and coincidence

2020 ◽  
Vol 35 (15) ◽  
pp. 2050123
Author(s):  
She-Sheng Xue
Keyword(s):  
Dark Matter ◽  
Acoustic Wave ◽  
Cosmological Constant ◽  
Einstein Equation ◽  
Large Scale ◽  
Particle Production ◽  
Cosmological Term ◽  
Coincidence Problem ◽  
Cosmic Inflation ◽  
Cosmic Coincidence Problem

We present a possible understanding to the issues of cosmological constant, inflation, dark matter and coincidence problems based only on the Einstein equation and Hawking particle production. The inflation appears and results agree to observations. The CMB large-scale anomaly can be explained and the dark-matter acoustic wave is speculated. The entropy and reheating are discussed. The cosmological term [Formula: see text] tracks down the matter [Formula: see text] until the radiation-matter equilibrium, then slowly varies, thus the cosmic coincidence problem can be avoided. The relation between [Formula: see text] and [Formula: see text] is shown and can be examined at large redshifts.

scholarly journals Exponential Cosmological Solutions with Three Different Hubble-Like Parameters in (1 + 3 + k1 + k2)-Dimensional EGB Model with a Λ-Term

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 250
Author(s):  
K. K. Ernazarov ◽  
V. D. Ivashchuk
Keyword(s):  
Lower Bounds ◽  
Gravitational Constant ◽  
Cosmological Term ◽  
Upper And Lower Bounds ◽  
Symmetry Groups ◽  
Exponential Time ◽  
Scale Factors ◽  
Exponential Expansion ◽  
Cosmological Solutions ◽  
Stable Solutions

A D-dimensional Einstein–Gauss–Bonnet model with a cosmological term Λ , governed by two non-zero constants: α 1 and α 2 , is considered. By restricting the metrics to diagonal ones, we study a class of solutions with the exponential time dependence of three scale factors, governed by three non-coinciding Hubble-like parameters: H > 0 , h 1 , and h 2 , obeying 3 H + k 1 h 1 + k 2 h 2 ≠ 0 and corresponding to factor spaces of dimensions: 3, k 1 > 1 , and k 2 > 1 , respectively, with D = 4 + k 1 + k 2 . The internal flat factor spaces of dimensions k 1 and k 2 have non-trivial symmetry groups, which depend on the number of compactified dimensions. Two cases: (i) 3 < k 1 < k 2 and (ii) 1 < k 1 = k 2 = k , k ≠ 3 , are analyzed. It is shown that in both cases, the solutions exist if α = α 2 / α 1 > 0 and α Λ > 0 obey certain restrictions, e.g., upper and lower bounds. In Case (ii), explicit relations for exact solutions are found. In both cases, the subclasses of stable and non-stable solutions are singled out. Case (i) contains a subclass of solutions describing an exponential expansion of 3 d subspace with Hubble parameter H > 0 and zero variation of the effective gravitational constant G.

CMB constraints on the thermal evolution with a decaying cosmological term

2012 ◽  
Author(s):  
Riou Nakamura ◽  
E. P. Berni A. Thushari ◽  
Mikio Ikeda ◽  
Masa-aki Hashimoto
Keyword(s):  
Thermal Evolution ◽  
Cosmological Term
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