scholarly journals QUINTESSENCE AND COSMIC ACCELERATION

2002 ◽  
Vol 11 (09) ◽  
pp. 1389-1397 ◽  
Author(s):  
M. K. MAK ◽  
T. HARKO
Keyword(s):  
Gravitational Field ◽  
Scalar Field ◽  
Field Potential ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Field Equations ◽  
Gravitational Field Equations ◽  
General Physical ◽  
Quintessence Field ◽  
The Universe

A cosmological model with perfect fluid and self-interacting quintessence field is considered in the framework of the spatially flat Friedmann–Robertson–Walker (FRW) geometry. By assuming that all physical quantities depend on the volume scale factor of the Universe, the general solution of the gravitational field equations can be expressed in an exact parametric form, with the volume taken as the parameter, and with the quintessence field as a free parameter. With an appropriate choice of the scalar field a class of exact parametric solutions is obtained, with an exponential type scalar field potential fixed via the gravitational field equations. The general physical behavior of the model is consistent with the recent cosmological scenario favored by supernova type Ia observations, indicating an accelerated expansion of the Universe.

Tsallis holographic dark energy models in axially symmetric space time

2020 ◽  
Vol 17 (01) ◽  
pp. 2050011 ◽  
Author(s):  
Vipin Chandra Dubey ◽  
Ambuj Kumar Mishra ◽  
Shikha Srivastava ◽  
Umesh Kumar Sharma
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Holographic Dark Energy ◽  
Field Potential ◽  
Accelerated Expansion ◽  
Anisotropic Universe ◽  
Axially Symmetric ◽  
Eos Parameter ◽  
Quintessence Field ◽  
The Universe

In this work, we have examined the behavior of Bianchi-I (axially symmetric) matter-dominated and the anisotropic Universe with the proposed dark energy, Tsallis holographic dark energy (THDE), with the Hubble horizon as infrared cut-off [Tavayef et al., Tsallis holographic dark energy, Phys. Lett. B 781 (2018) 195–200]. The Universe evolution from matter-dominated epoch to dark energy dominated epoch is described by our proposed THDE model. The EoS parameter in our THDE model explains the evolution of the Universe according to the value of nonextensive or Tsallis parameter [Formula: see text], phantom era ([Formula: see text]) or quintom (phantom line crossing) and the quintessence era ([Formula: see text]), before reaching to completely dark energy-dominated era in the future. Additionally, we also plan to reconcile the dark energy by the method of reconstructing the evolution of the scalar field potential. For the analysis, we take into account the quintessence field and phantom scalar field for this reconstruction, which at present shows the accelerated expansion.

scholarly journals Einstein-aether theory in Weyl integrable geometry

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Andronikos Paliathanasis ◽  
Genly Leon ◽  
John D. Barrow
Keyword(s):  
Gravitational Field ◽  
Field Equation ◽  
Scalar Field ◽  
Field Model ◽  
Affine Connection ◽  
Dynamical Evolution ◽  
Field Equations ◽  
Gravitational Field Equation ◽  
Gravitational Field Equations ◽  
Geometric Origin

AbstractWe study the Einstein-aether theory in Weyl integrable geometry. The scalar field which defines the Weyl affine connection is introduced in the gravitational field equation. We end up with an Einstein-aether scalar field model where the interaction between the scalar field and the aether field has a geometric origin. The scalar field plays a significant role in the evolution of the gravitational field equations. We focus our study on the case of homogeneous and isotropic background spacetimes and study their dynamical evolution for various cosmological models.

Kaluza–Klein minimally interacting dark energy model in the presence of massive scalar field

2021 ◽  
Vol 36 (08) ◽  
pp. 2150054
Author(s):  
K. Dasu Naidu ◽  
Y. Aditya ◽  
R. L. Naidu ◽  
D. R. K. Reddy
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Massive Scalar ◽  
Field Equations ◽  
Eos Parameter ◽  
Massive Scalar Field ◽  
The Universe ◽  
Kaluza Klein

In this paper, our purpose is to discuss the dynamical aspects of Kaluza–Klein five-dimensional cosmological model filled with minimally interacting baryonic matter and dark energy (DE) in the presence of an attractive massive scalar field. We obtain a determinate solution of the Einstein field equations using (i) a relation between the metric potentials and (ii) a power law relation between the average scale factor of the universe and the massive scalar field. We have determined scalar field, matter energy density, DE density, equation of state (EoS) [Formula: see text], deceleration [Formula: see text] and statefinder [Formula: see text] parameters of our model. We also develop [Formula: see text]–[Formula: see text] phase, squared sound speed, statefinders and [Formula: see text]–[Formula: see text] planes in the evolving universe. It is observed that the EoS parameter exhibits quintom-like behavior from quintessence to phantom epoch by crossing the vacuum era of the universe. The squared speed of sound represents the instability of the model, whereas the [Formula: see text]–[Formula: see text] plane shows both thawing and freezing regions. The [Formula: see text]CDM limit is attained in both [Formula: see text]–[Formula: see text] and statefinder planes. We have also discussed the cosmological importance of the above parameters with reference to modern cosmology. It is found that the dynamics of these cosmological parameters indicate the accelerated expansion of the universe which is consistent with the current cosmological observations.

scholarly journals Exact scalar–tensor cosmological models

2017 ◽  
Vol 26 (07) ◽  
pp. 1750073 ◽  
Author(s):  
J. A. Belinchón ◽  
T. Harko ◽  
M. K. Mak
Keyword(s):  
Scalar Field ◽  
Cosmological Solution ◽  
Gravitational Theory ◽  
Field Equations ◽  
Group Approach ◽  
Gravitational Field Equations ◽  
Gravitational Theories ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

Scalar–tensor gravitational theories are important extensions of standard general relativity, which can explain both the initial inflationary evolution, as well as the late accelerating expansion of the universe. In the present paper, we investigate the cosmological solution of a scalar–tensor gravitational theory, in which the scalar field [Formula: see text] couples to the geometry via an arbitrary function [Formula: see text]. The kinetic energy of the scalar field as well as its self-interaction potential [Formula: see text] are also included in the gravitational action. By using a standard mathematical procedure, the Lie group approach, and Noether symmetry techniques, we obtain several exact solutions of the gravitational field equations describing the time evolutions of a flat Friedman–Robertson–Walker universe in the framework of the scalar–tensor gravity. The obtained solutions can describe both accelerating and decelerating phases during the cosmological expansion of the universe.

scholarly journals Inflation in anisotropic brane universe using tachyon field

2019 ◽  
Vol 28 (13) ◽  
pp. 1941010 ◽  
Author(s):  
Rikpratik Sengupta ◽  
Prasenjit Paul ◽  
Bikash Chandra Paul ◽  
Saibal Ray
Keyword(s):  
Gravitational Field ◽  
Cosmological Solution ◽  
Tachyon Field ◽  
Field Equations ◽  
Tachyonic Field ◽  
Bianchi I ◽  
Gravitational Field Equations ◽  
First Case ◽  
Cosmological Scenario ◽  
The Universe

Cosmological solution to the gravitational field equations in the generalized Randall–Sundrum model for an anisotropic brane with Bianchi-I geometry and perfect fluid as matter sources has been considered. The matter on the brane is described by a tachyonic field. The solution admits inflationary era and at a later epoch the anisotropy of the universe washes out. We obtain two classes of cosmological scenario: in the first case, universe evolves from singularity and in the second case, universe expands without singularity.

Kantowski–Sachs universe with dark energy fluid and massive scalar field

2020 ◽  
Vol 98 (11) ◽  
pp. 993-998
Author(s):  
K. Deniel Raju ◽  
M.P.V.V. Bhaskara Rao ◽  
Y. Aditya ◽  
T. Vinutha ◽  
D.R.K. Reddy
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Massive Scalar ◽  
Field Equations ◽  
Massive Scalar Field ◽  
Anisotropic Dark Energy ◽  
Expansion Of The Universe ◽  
The Universe

This study is mainly concerned with a spatially homogeneous and anisotropic Kantowski–Sachs cosmological model with anisotropic dark energy fluid and massive scalar field. We solve the field equations using (i) the shear scalar proportionality to the expansion scalar and (ii) a mathematical condition that is a consequence of the power law between the scalar field and the average scale factor of the universe, and the corresponding dark energy model is presented. The cosmological parameters of the model are computed and discussed, as well as the relevance of its dynamical aspects to the recent scenario of the accelerated expansion of the universe.

Inhomogeneous viscous fluid cosmological model of the universe with effective equation of state and scalar field

2018 ◽  
Vol 15 (05) ◽  
pp. 1850078
Author(s):  
G. S. Khadekar ◽  
Rupali Talole
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Dynamical Equation ◽  
Field Potential ◽  
Scale Factor ◽  
Field Equations ◽  
Effective Equation ◽  
Expansion Formula ◽  
Dependent Parameter ◽  
The Universe

A generalized dynamical equation for the scale factor of the universe is proposed to describe the cosmological evolution by considering the bulk viscosity [Formula: see text] and time dependent parameter [Formula: see text] as linear combination of two terms of the form [Formula: see text] and [Formula: see text] i.e. one is constant and other is proportional to the scalar expansion [Formula: see text] In this framework, we obtained the analytical solution of the field equations for the scale factor [Formula: see text] scalar field potential [Formula: see text] with effective equation of state (EoS) of the form [Formula: see text] where [Formula: see text]. The final results are compared with previously known results for the model with scalar field.

scholarly journals Noether symmetries of Einstein-aether scalar field cosmology

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Yusuf Kucukakca ◽  
Amin Rezaei Akbarieh
Keyword(s):  
Scalar Field ◽  
Noether Symmetry ◽  
Accelerated Expansion ◽  
Noether Symmetries ◽  
Field Equations ◽  
Symmetry Approach ◽  
Expansion Of The Universe ◽  
Frw Metric ◽  
Scalar Field Cosmology ◽  
The Universe

AbstractIn this paper, we explore an Einstein-aether cosmological model by adding the scalar field in which it has an interaction with the aether field. For the cosmological implications of the model, we consider that the universe can be described by the spatially flat FRW metric together with the matter dominated universe. Applying Noether symmetry approach to the point-like Lagrangian we determine the explicit forms of unknown functions i.e. the potential and coupling function. We solve the analytical cosmological solutions of the field equations admitting the Noether symmetry, basically divided into two parts. Our results show that the obtained solutions lead to an accelerated expansion of the universe. We also discuss the tensor perturbations within the framework of this model in order to get information about the mass of gravitational waves.

scholarly journals Stability of a Noncanonical Scalar Field Model during Cosmological Date

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Z. Ossoulian ◽  
T. Golanbari ◽  
H. Sheikhahmadi ◽  
Kh. Saaidi
Keyword(s):  
Fixed Point ◽  
Scalar Field ◽  
Energy Density ◽  
Field Model ◽  
Field Potential ◽  
Linear Perturbation ◽  
Field Equations ◽  
Gravitational Fields ◽  
The Universe ◽  
Nonlinear Field Equations

Using the noncanonical model of scalar field, the cosmological consequences of a pervasive, self-interacting, homogeneous, and rolling scalar field are studied. In this model, the scalar field potential is “nonlinear” and decreases in magnitude with increasing the value of the scalar field. A special solution of the nonlinear field equations ofϕthat has time dependency as fixed point is obtained. The fixed point relies on the noncanonical term of action andγ-parameter; this parameter appeared in energy density of scalar field redshift. By means of such fixed point the different eigenvalues of the equation of motion will be obtained. In different epochs in the evolution of the Universe for different values ofqandn, the potentials as a function of scalar field are attained. The behavior of baryonic perturbations in linear perturbation scenario as a considerable amount of energy density of scalar field at low redshifts prevents the growth of perturbations in the ordinary matter fluid. The energy density in the scalar field is not appreciably perturbed by nonrelativistic gravitational fields, in either the radiation or matter dominant or scalar field dominated epoch.

scholarly journals INFLATIONARY SOLUTIONS WITH A FIVE-DIMENSIONAL COMPLEX SCALAR FIELD

2006 ◽  
Vol 21 (05) ◽  
pp. 409-419
Author(s):  
J. J. VAN DER BIJ ◽  
EUGEN RADU
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Accelerated Expansion ◽  
Complex Scalar ◽  
Dimensional Spacetime ◽  
Klein Gordon ◽  
Expansion Of The Universe ◽  
Complex Scalar Field ◽  
New Feature ◽  
The Universe

We discuss inflationary solutions of the coupled Einstein–Klein–Gordon equations for a complex field in a five-dimensional spacetime with a compact x5 dimension. As a new feature, the scalar field contains a dependence on the extra dimension of the form exp (imx5), corresponding to Kaluza–Klein excited modes. In a four-dimensional picture, a nonzero m implies the presence of a new term in the scalar field potential. An interesting feature of these solutions is the possible existence of several periods of oscillation of the scalar field around the equilibrium value at the minimum of the potential. These oscillations lead to cosmological periods of accelerated expansion of the universe.

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