scholarly journals A THEORY OF TIME-VARYING CONSTANTS

2001 ◽  
Vol 10 (03) ◽  
pp. 299-309 ◽  
Author(s):  
JOSÉ ANTONIO BELINCHÓN ◽  
ANTONIO ALFONSO-FAUS
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Cosmological Model ◽  
Perfect Fluid ◽  
Gauge Invariance ◽  
Time Varying ◽  
Field Equations ◽  
Cosmological Time ◽  
Varying Constants ◽  
Time Varying Constants

We present a flat (K=0) cosmological model, described by a perfect fluid with the "constants" G, c and Λ varying with cosmological time t. We introduce Planck's "constant" ℏ in the field equations through the equation of state for the energy density of radiation. We then determine the behaviour of the "constants" by using the zero divergence of the second member of the modified Einstein's field equations i.e. div [Formula: see text], together with the equation of state and the Einstein cosmological equations. Assuming realistic physical and mathematical conditions we obtain a consistent result with ℏ c= constant . In this way we obtain gauge invariance for the Schrödinger equation and the behavior of the remaining "constants."

scholarly journals PERFECT FLUID COSMOLOGICAL MODELS WITH TIME-VARYING CONSTANTS

2003 ◽  
Vol 12 (06) ◽  
pp. 1113-1129 ◽  
Author(s):  
JOSÉ ANTONIO BELINCHÓN ◽  
INDRAJIT CHAKRABARTY
Keyword(s):  
Cosmological Model ◽  
Perfect Fluid ◽  
Fluid Model ◽  
Time Varying ◽  
Bulk Viscous Fluid ◽  
Bulk Viscous ◽  
Varying Constants ◽  
Time Varying Constants ◽  
Limiting Case ◽  
Symmetry Method

In this paper, we study in detail a perfect fluid cosmological model with time-varying "constants" using dimensional analysis and the symmetry method. We examine the case of variable "constants" in detail without considering the perfect fluid model as a limiting case of a model with a causal bulk viscous fluid as discussed in a recent paper. We obtain some new solutions through the Lie method and show that when matter creation is considered, these solutions are physically relevant.

scholarly journals Bianchi I in scalar and scalar-tensor cosmologies

Open Physics ◽  
2012 ◽  
Vol 10 (4) ◽  
Author(s):  
José Belinchón
Keyword(s):  
Perfect Fluid ◽  
Theoretical Models ◽  
Point Of View ◽  
Time Varying ◽  
Self Similarity ◽  
Bianchi I ◽  
Exact Power ◽  
Varying Constants ◽  
Time Varying Constants ◽  
Matter Fields

AbstractWe study how the constants G and Λ may vary in different theoretical models (general relativity (GR) with a perfect fluid, scalar cosmological models (SM) (“quintessence”) with and without interacting scalar and matter fields and three scalar-tensor theories (STT) with a dynamical Λ) in order to explain some observational results. We apply the program outlined in section II to study the Bianchi I models, under the self-similarity hypothesis. We put special emphasis on calculating exact power-law solutions which allow us to compare the different models. In all the studied cases we conclude that the solutions are isotropic and noninflationary. We also arrive at the conclusion that in the GR model with time-varying constants, Λ vanishes while G is constant. In the SM all the solutions are massless i.e. the potential vanishes and all the interacting models are inconsistent from the thermodynamical point of view. The solutions obtained in the STT collapse to the perfect fluid one obtained in the GR model where G is a true constant and Λ vanishes as in the GR and SM frameworks.

scholarly journals FULL CAUSAL BULK VISCOUS COSMOLOGIES WITH TIME-VARYING CONSTANTS

2003 ◽  
Vol 12 (05) ◽  
pp. 861-883 ◽  
Author(s):  
JOSÉ ANTONIO BELINCHÓN ◽  
INDRAJIT CHAKRABARTY
Keyword(s):  
Equations Of State ◽  
Functional Dependence ◽  
Physical Parameters ◽  
Time Varying ◽  
Field Equations ◽  
Bulk Viscous ◽  
Varying Constants ◽  
Time Varying Constants ◽  
Viscous Pressure ◽  
Bulk Viscous Pressure

We study the evolution of a flat Friedmann–Robertson–Walker Universe, filled with a bulk viscous cosmological fluid, in the presence of time varying "constants." The dimensional analysis of the model suggests a proportionality between the bulk viscous pressure of the dissipative fluid and the energy density. Using this assumption and with the choice of the standard equations of state for the bulk viscosity coefficient, temperature and relaxation time, the general solution of the field equations can be obtained, with all physical parameters having a power-law time dependence. The symmetry analysis of this model, performed using Lie group techniques, confirms the uniqueness of the solution for this functional form of the bulk viscous pressure. In order to find another possible solution we relax the hypotheses and assume a concrete functional dependence for the "constants."

HOMOGENEOUS PERFECT FLUID IN BRANS-DICKE-BIANCHI TYPE V COSMOLOGICAL MODEL

1996 ◽  
Vol 05 (01) ◽  
pp. 65-69 ◽  
Author(s):  
SUBENOY CHAKRABORTY ◽  
GOPAL CH. NANDY
Keyword(s):  
Equation Of State ◽  
Cosmological Model ◽  
Perfect Fluid ◽  
Analytical Solutions ◽  
Bianchi Type ◽  
Field Equations ◽  
Type V ◽  
Bianchi Type V

In this paper we have studied homogeneous perfect fluid for the Bianchi type V model in the Brans-Dicke theory. The equation of state is assumed to be [Formula: see text]. Some analytical solutions to the field equations are obtained for the radiation era.

Charged anisotropic static cylindrically symmetric models

2013 ◽  
Vol 91 (2) ◽  
pp. 113-119 ◽  
Author(s):  
M. Sharif ◽  
H. Ismat Fatima
Keyword(s):  
Electromagnetic Field ◽  
Equation Of State ◽  
Energy Density ◽  
Symmetric Space ◽  
Radial Pressure ◽  
Matter Distribution ◽  
Field Equations ◽  
Stellar Objects ◽  
Cylindrically Symmetric ◽  
Barotropic Equation

In this paper, we investigate exact solutions of the field equations for charged, anisotropic, static, cylindrically symmetric space–time. We use a barotropic equation of state linearly relating the radial pressure and energy density. The analysis of the matter variables indicates a physically reasonable matter distribution. In the most general case, the central densities correspond to realistic stellar objects in the presence of anisotropy and charge. Finally, we conclude that matter sources are less affected by the electromagnetic field.

Anisotropic Dark Energy Cosmological Model with Cosmic Strings

2020 ◽  
Author(s):  
T. Vinutha ◽  
V.U.M. Rao ◽  
Molla Mengesha
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Model ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Physical Parameters ◽  
Type I ◽  
Field Equations ◽  
Eos Parameter ◽  
Phantom Divide

The present study deals with a spatially homogeneous locally rotationally symmetric (LRS) Bianchi type-I dark energy cosmological model containing one dimensional cosmic string fluid source. The Einstein's field equations are solved by using a relation between the metric potentials and hybrid expansion law of average scale factor. We discuss accelerated expansion of our model through equation of state (ωde) and deceleration parameter (q). We observe that in the evolution of our model, the equation of state parameter starts from matter dominated phase ωde > -1/3 and ultimately attains a constant value in quintessence region (-1 < ωde < -1/3). The EoS parameter of the model never crosses the phantom divide line (ωde = 1). These facts are consistent with recent observations. We also discuss some other physical parameters.

scholarly journals GENERALIZED MODEL FOR Λ DARK ENERGY

2009 ◽  
Vol 18 (03) ◽  
pp. 389-396 ◽  
Author(s):  
UTPAL MUKHOPADHYAY ◽  
P. C. RAY ◽  
SAIBAL RAY ◽  
S. B. DUTTA CHOUDHURY
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Model ◽  
A Priori ◽  
State Parameter ◽  
Spherically Symmetric ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Equation Of State Parameter ◽  
Two Fluid

Einstein field equations under spherically symmetric space–times are considered here in connection with dark energy investigation. A set of solutions is obtained for a kinematic Λ model, viz. [Formula: see text], without assuming any a priori value for the curvature constant and the equation-of-state parameter ω. Some interesting results, such as the nature of cosmic density Ω and deceleration parameter q, have been obtained with the consideration of two-fluid structure instead of the usual unifluid cosmological model.

Sign in / Sign up

Export Citation Format

Share Document