Evolution of anisotropic cosmic models in f(R,ϕ) gravity

2018 ◽  
Vol 27 (12) ◽  
pp. 1850115 ◽  
Author(s):  
M. Zubair ◽  
Farzana Kousar ◽  
Saira Waheed
Keyword(s):  
Scalar Field ◽  
Power Law ◽  
Bianchi Type ◽  
Scalar Potential ◽  
Anisotropic Fluid ◽  
Type I ◽  
Field Equations ◽  
Eos Parameter ◽  
Free Parameters ◽  
Physical Quantities

In this paper, we will discuss cosmological models using Bianchi type I for anisotropic fluid in [Formula: see text] theory of gravity which involves scalar potential. For this purpose, we consider power law assumptions of coupling function and scalar field along with the proportionality condition of expansion and shear scalars. We choose two [Formula: see text] models and obtain exact solutions of field equations in both cases. For these constructed models, the behavior of different physical quantities like EoS parameter, self-interacting potential as well as deceleration and skewness parameters are explored and illustrated graphically for the feasible ranges of free parameters. It is concluded that anisotropic fluid approaches isotropy in later cosmic times for both models.

Power law inflation with anisotropic fluid in Lyra’s manifold

2017 ◽  
Vol 95 (8) ◽  
pp. 748-752 ◽  
Author(s):  
S. Surendra Singh ◽  
Y. Bembem Devi ◽  
M. Saratchandra Singh
Keyword(s):  
Power Law ◽  
Bianchi Type ◽  
Anisotropic Fluid ◽  
Type I ◽  
Field Equations ◽  
Volumetric Expansion ◽  
Lyra’S Manifold ◽  
Rotationally Symmetric ◽  
Age Of The Universe ◽  
The Universe

Field equations of the locally rotationally symmetric (LRS) Bianchi type-I metric with anisotropic fluid are constructed within the framework of Lyra’s manifold. Power-law volumetric expansion is used to obtain exact solutions of the models for constant and time-dependent displacement field. We discuss the asymptotic behaviors of the derived models, anisotropic behavior of the fluid, expansion parameter, and the evolution of the model with the age of the universe.

scholarly journals Warm inflation with non-comoving scalar field and radiation fluid

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Tiberiu Harko ◽  
Haidar Sheikhahmadi
Keyword(s):  
Scalar Field ◽  
Anisotropic Fluid ◽  
Type I ◽  
Field Equations ◽  
Warm Inflation ◽  
Inflationary Scenario ◽  
Radiation Generation ◽  
Theoretical Predictions ◽  
Field Radiation ◽  
Basic Equations

AbstractWe consider a warm inflationary scenario in which the two major fluid components of the early Universe, the scalar field and the radiation fluid, evolve with distinct four-velocities. This cosmological configuration is equivalent to a single anisotropic fluid, expanding with a four-velocity that is a combination of the two fluid four-velocities. Due to the presence of anisotropies the overall cosmological evolution is also anisotropic. We obtain the gravitational field equations of the non-comoving scalar field–radiation mixture for a Bianchi Type I geometry. By assuming the decay of the scalar field, accompanied by a corresponding radiation generation, we formulate the basic equations of the warm inflationary model in the presence of two non-comoving components. By adopting the slow-roll approximation the theoretical predictions of the warm inflationary scenario with non-comoving scalar field and radiation fluid are compared in detail with the observational data obtained by the Planck satellite in both weak dissipation and strong dissipation limits, and constraints on the free parameters of the model are obtained. The functional forms of the scalar field potentials compatible with the non-comoving nature of warm inflation are also obtained.

A new class of holographic dark energy models in LRS Bianchi Type-I

2021 ◽  
Author(s):  
Anirudh Pradhan ◽  
Vinod Kumar Bhardwaj ◽  
Archana Dixit ◽  
Syamala Krishnannair
Keyword(s):  
Dark Energy ◽  
Bianchi Type ◽  
Holographic Dark Energy ◽  
Cosmological Solution ◽  
Type I ◽  
Field Equations ◽  
Eos Parameter ◽  
Bianchi Type I ◽  
New Class ◽  
Energy Models

In this paper, we examine the LRS Bianchi-type-I cosmological model with holographic dark energy. The exact solutions to the corresponding field equations are obtained by using the generalized hybrid expansion law (HEL). The EoS parameter [Formula: see text] for DE is found to be time-dependent and redshift-dependent and its exiting range for derived model is agreeing well with the current observations. Here, we likewise apply two mathematical diagnostics, the statefinders ([Formula: see text]) and [Formula: see text] plan to segregate HDE model from the [Formula: see text]CDM model. Here, the [Formula: see text] diagnostic trajectories are good tools to classify the dynamical DE model. We found that our model lies in both thawing region and freezing region. We also construct the potential as well as dynamics of the quintessence and tachyon scalar field. Some physical and geometric properties of this model along with the physical acceptability of cosmological solution have been discussed in detail.

Scalar fields in f(G) gravity

2020 ◽  
Vol 17 (09) ◽  
pp. 2050132
Author(s):  
Dog̃ukan Taṣer ◽  
Melis Ulu Dog̃ru
Keyword(s):  
Scalar Field ◽  
Bianchi Type ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Type I ◽  
Massless Scalar Field ◽  
Field Equations ◽  
Massive Scalar Field ◽  
Scalar Field Models ◽  
Bianchi Type I Universe

In this study, we investigated scalar field in [Formula: see text]-gravity by using LRS Bianchi type-I universe. Massless and massive scalar field models are separately constructed in [Formula: see text]-gravity. Massless scalar field models are examined in the cases of constant and exponential potential fields. For all models, solutions of field equations are obtained under the consideration of [Formula: see text]. [Formula: see text] functions for each model are separately attained in theory. It is shown that constructed models in the presence of massless scalar field permit quintessence scalar field. Also, it is observed that each model indicates expanding universe with deceleration. Also, kinematical quantities are analyzed in the light of obtained solutions. All models are concluded with a geometric and physical perspective.

scholarly journals LRS Bianchi Type-I Inflationary String Cosmological Model in Brans-Dicke Theory of Gravitation

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
R. Venkateswarlu ◽  
J. Satish
Keyword(s):  
Scalar Field ◽  
Cosmological Model ◽  
Power Law ◽  
Bianchi Type ◽  
Type I ◽  
Physical Behavior ◽  
Bianchi Type I ◽  
Expansion Scalar ◽  
Theory Of Gravitation ◽  
Shear Scalar

We investigate locally rotational symmetric (LRS) Bianchi type I space time coupled with scalar field. String cosmological models generated by a cloud of strings with particles attached to them are studied in the Brans-Dicke theory. We assume that the expansion scalar is proportional to the shear scalar and also power law ansatz for scalar field. The physical behavior of the resulting model is discussed through different parameters.

scholarly journals Bianchi Type-I Dark Energy Cosmology with Power-Law Relation in Brans-Dicke Theory of Gravitation

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
S. D. Katore ◽  
D. V. Kapse
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Power Law ◽  
Bianchi Type ◽  
Type I ◽  
Field Equations ◽  
Coincidence Problem ◽  
Bianchi Type I ◽  
Interacting Dark Energy ◽  
Theory Of Gravitation

We have studied the interacting and non-interacting dark energy and dark matter in the spatially homogenous and anisotropic Bianchi type-I model in the Brans-Dicke theory of gravitation. The field equations have been solved (i) by using power-law relation and (ii) by assuming scale factor in terms of redshift. Here we have considered two cases of an interacting and non-interacting dark energy scenario and obtained general results. It has been found that for suitable choice of interaction between dark energy and dark matter we can avoid the coincidence problem which appears in the ΛCDM model. Some physical aspects and stability of the models are discussed in detail. The statefinder diagnostic pair, i.e., {r,s}, is adopted to differentiate our dark energy models.

scholarly journals Weak and strong warm logamediate anisotropic inflationary universe model

2020 ◽  
Vol 98 (11) ◽  
pp. 1029-1038
Author(s):  
Wajiha Javed ◽  
Iqra Nawazish ◽  
Mohsin Raza Khan ◽  
Ali Övgün
Keyword(s):  
Bianchi Type ◽  
Scalar Potential ◽  
Cosmological Parameters ◽  
Chaplygin Gas ◽  
Inflationary Universe ◽  
Type I ◽  
Field Equations ◽  
Warm Inflation ◽  
Slow Roll ◽  
Rotationally Symmetric

In this paper we investigate a warm inflation scenario of a locally rotationally symmetric Bianchi type-I model using a background of modified Chaplygin gas. We determine the field equations and perturbations parameters, such as the scalar power spectrum, scalar spectral index, scalar potential, and tensor-to-scalar ratio under the slow roll approximation. We determine these parameters in the direction of the Hubble parameter during both the weak and strong logamediate inflationary regimes. These cosmological parameters show that the anisotropic model is compatible with WMAP 7 from the 2018 Planck observational data.

scholarly journals Anisotropic solution in phantom cosmology via Noether symmetry approach

2018 ◽  
Vol 96 (7) ◽  
pp. 677-680 ◽  
Author(s):  
I. Basaran Oz ◽  
Y. Kucukakca ◽  
N. Unal
Keyword(s):  
Scalar Field ◽  
Bianchi Type ◽  
Space Time ◽  
Noether Symmetry ◽  
Type I ◽  
Field Equations ◽  
Anisotropic Solution ◽  
Bianchi Type I ◽  
Symmetry Approach ◽  
The Universe

In this study, we consider a phantom cosmology in which a scalar field is minimally coupled to gravity. For anisotropic locally rotational symmetric (LRS) Bianchi type I space–time, we use the Noether symmetry approach to determine the potential of such a theory. It is shown that the potential must be in the trigonometric form as a function of the scalar field. We solved the field equations of the theory using the result obtained from the Noether symmetry. Our solution shows that the universe has an accelerating expanding phase.

scholarly journals Anisotropic power-law inflation in a two-scalar-field model with a mixed kinetic term

2017 ◽  
Vol 26 (07) ◽  
pp. 1750072 ◽  
Author(s):  
Tuan Q. Do ◽  
Sonnet Hung Q. Nguyen
Keyword(s):  
Scalar Field ◽  
Power Law ◽  
Field Model ◽  
Scalar Fields ◽  
Kinetic Term ◽  
Type I ◽  
Field Equations ◽  
Scalar Field Model ◽  
Phantom Scalar ◽  
The Stability

We examine whether an extended scenario of a two-scalar-field model, in which a mixed kinetic term of canonical and phantom scalar fields is involved, admits the Bianchi type I metric, which is homogeneous but anisotropic spacetime, as its power-law solutions. Then, we analyze the stability of the anisotropic power-law solutions to see whether these solutions respect the cosmic no-hair conjecture or not during the inflationary phase. In addition, we will also investigate a special scenario, where the pure kinetic terms of canonical and phantom fields disappear altogether in field equations, to test again the validity of cosmic no-hair conjecture. As a result, the cosmic no-hair conjecture always holds in both these scenarios due to the instability of the corresponding anisotropic inflationary solutions.

Scalar field solutions for anisotropic universe models in various gravitation theories

2020 ◽  
Vol 17 (02) ◽  
pp. 2050025
Author(s):  
Ali Kabak ◽  
Sezgin Aygün
Keyword(s):  
Scalar Field ◽  
Bianchi Type ◽  
Scalar Potential ◽  
Anisotropic Universe ◽  
Type I ◽  
Bianchi Type I ◽  
Phantom Scalar ◽  
Bianchi Type I Universe ◽  
Phantom Scalar Field ◽  
Universe Models

In this study, we have investigated homogeneous and anisotropic Marder and Bianchi type I universe models filled with normal and phantom scalar field matter distributions with [Formula: see text] in [Formula: see text] gravitation theory (T. Harko et al., Phys. Rev. D 84 (2011) 024020). In this model, [Formula: see text] is the Ricci scalar and [Formula: see text] is the trace of energy–momentum tensor. To obtain exact solutions of modified field equations, we have used anisotropy feature of the universe and different scalar potential models with [Formula: see text] function. Also, we have obtained general relativity (GR) solutions for normal and phantom scalar field matter distributions in Marder and Bianchi type I universes. Additionally, we obtained the same scalar function values by using different scalar field potentials for Marder and Bianchi type I universe models with constant difference in [Formula: see text] gravity and GR theory. From obtained solutions, we get negative cosmological term value for [Formula: see text] constant scalar potential model with Marder and Bianchi type I universes in GR theory. These results agree with the studies of Maeda and Ohta, Aktaş et al. also Biswas and Mazumdar. Finally, we have discussed and compared our results in gravitation theories.

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