scholarly journals Massless fermions in planar Bianchi-type-I universes: exact and approximate solutions

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Matthias Wollensak
Keyword(s):  
Exact Solution ◽  
Bianchi Type ◽  
Approximate Solutions ◽  
Equivalence Classes ◽  
Type I ◽  
Bianchi Type I ◽  
Scale Factors ◽  
Two Parameters ◽  
Formal Solutions ◽  
Massless Fermions

AbstractBased upon the exact formal solutions of the Weyl–Dirac-equation in anisotropic planar Bianchi-type-I background spacetimes with power law scale factors, one can introduce suitable equivalence classes of the solutions of these models. The associated background spacetimes are characterized by two parameters. It is shown that the exact solutions of all models of a given equivalence class can be generated with the help of a special transformation of these two parameters, provided one knows a single exact solution of an arbitrary member of this class. The method can also be utilized to derive approximate solutions, i.e. solutions which exhibit the correct behavior at early and at late times as well. This is explicitly demonstrated for the case of the anisotropic Kasner background with axial symmetry.

scholarly journals Approximate Solutions of the LRS Bianchi Type-I Cosmological Model

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 403
Author(s):  
Yihu Feng ◽  
Lei Hou
Keyword(s):  
Cosmological Model ◽  
Homotopy Perturbation Method ◽  
Bianchi Type ◽  
Approximate Solutions ◽  
Space Time ◽  
Type I ◽  
Main Field ◽  
Field Equations ◽  
Bianchi Type I ◽  
Homotopy Perturbation

In this current study, we explore the modified homogeneous cosmological model in the background of LRS Bianchi type-I space–time. For this purpose, we employ the Homotopy Perturbation Method (HPM). HPM is an analytical-based method. Further, we calculated the main field equations of the cosmological model LRS Bianchi type-I space–time. Furthermore, we discuss the necessary calculations of HPM. Therefore, we investigate the analytical solution of our problem by adopting HPM. In this response, we discuss five different values of parameter n. We also give a brief discussion about solutions. The main purpose of this study is to apply the application of HPM in the cosmological field.

Classical and quantum cosmological solutions in Bianchi type-I metric with fermionic field and relativistic fluid in Schutz’s formalism

2019 ◽  
Vol 34 (33) ◽  
pp. 1950271 ◽  
Author(s):  
Marlos O. Ribas ◽  
Fernando P. Devecchi ◽  
Gilberto M. Kremer
Keyword(s):  
Degrees Of Freedom ◽  
Bianchi Type ◽  
Hamiltonian Formalism ◽  
Inflationary Universe ◽  
Type I ◽  
Conformal Time ◽  
Fermionic Field ◽  
Bianchi Type I ◽  
Relativistic Fluid ◽  
Scale Factors

A model for an anisotropic pre-inflationary universe described by the Bianchi type-I metric is developed. A relativistic fluid of the Schutz formalism and a self-interacting fermionic field are considered as sources of the gravitational field. The classical analysis is based on the Hamiltonian formalism written in terms of the Misner variables and it is shown that the fluid degrees of freedom can be embodied by a conformal time variable. The three classical scale factors are obtained as functions of the conformal time. The quantum analysis follows from the de Broglie–Bohm formalism applied to the wave function which is a solution of the Wheeler–DeWitt equation and the three scale factors are also determined as functions of the conformal time. While the classical expressions for the scale factors show a singularity when the conformal time vanishes, their quantum expressions exhibit bouncing behavior. It is possible to adjust the behavior of the classical and quantum scale factors as functions of the conformal time so that they have a common isotropic behavior at late times with a dilution of the quantum effects.

Stability of LRS Bianchi type-I cosmological models in f(R, T)-gravity

2019 ◽  
Vol 19 (4) ◽  
pp. 055 ◽  
Author(s):  
Umesh Kumar Sharma ◽  
Rashid Zia ◽  
Anirudh Pradhan ◽  
Aroon Beesham
Keyword(s):  
Bianchi Type ◽  
Cosmological Models ◽  
Type I ◽  
Bianchi Type I

Energy–momentum distributions of Ruban universe in general relativity and teleparallel gravity

2019 ◽  
Vol 34 (03n04) ◽  
pp. 1950011 ◽  
Author(s):  
C. Aktaş
Keyword(s):  
General Relativity ◽  
Bianchi Type ◽  
Teleparallel Gravity ◽  
Type I ◽  
Universe Model ◽  
Zero Energy ◽  
Bianchi Type I ◽  
Momentum Distributions ◽  
Bianchi Type I Universe

In this study, we obtain Einstein, Bergmann–Thomson (BT), Landau–Lifshitz (LL), Møller, Papapetrou (PP) and Tolman energy–momentum (EM) distributions for Ruban universe model in general relativity (GR) and teleparallel gravity (TG). We obtain same results for Einstein, Bergmann–Thomson and Landau–Lifshitz energy–momentum distributions in GR and TG. Also, we get same results for Einstein and Tolman energy–momentum distributions in GR. The Møller energy–momentum results are different in GR and TG. Also, using Ruban universe model, we obtain LRS Bianchi type I solutions and we get zero energy–momentum results for this universe model in GR and TG. These results of LRS Bianchi type I universe model agree with Aygün et al., Taşer et al., Doğru et al., Banerjee–Sen, Tryon and Xulu in different gravitation theories.

Bianchi Type I String Dust Magnetized Cosmological Models in Lyra Geometry

2010 ◽  
Vol 54 (1) ◽  
pp. 197-202 ◽  
Author(s):  
Raj Bali ◽  
Naresh K Chandnani ◽  
Lokesh Kumar Gupta
Keyword(s):  
Bianchi Type ◽  
Lyra Geometry ◽  
Cosmological Models ◽  
Type I ◽  
Bianchi Type I
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