scholarly journals Generalized scalar field potentials and inflation

1995 ◽  
Vol 51 (12) ◽  
pp. 6757-6763 ◽  
Author(s):  
Paul Parsons ◽  
John D. Barrow
Keyword(s):  
Scalar Field ◽  
Field Potentials

scholarly journals Dynamics of scalar potentials in theory of gravity

2019 ◽  
Vol 97 (8) ◽  
pp. 880-894
Author(s):  
M. Zubair ◽  
Farzana Kousar ◽  
Saira Waheed
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Graphical Analysis ◽  
Chaplygin Gas ◽  
Field Potentials ◽  
De Sitter ◽  
Field Equations ◽  
Barotropic Fluid ◽  
First Case ◽  
De Sitter Universe

In this paper, we explore the nature of scalar field potential in [Formula: see text] gravity using a well-motivated reconstruction scheme for flat Friedmann–Robertson–Walker (FRW) geometry. The beauty of this scheme lies in the assumption that the Hubble parameter can be expressed in terms of scalar field and vice versa. Firstly, we develop field equations in this gravity and present some general explicit forms of scalar field potential via this technique. In the first case, we take the de Sitter universe model and construct some field potentials by taking different cases for the coupling function. In the second case, we derive some field potentials using the power law model in the presence of different matter sources like barotropic fluid, cosmological constant, and Chaplygin gas for some coupling functions. From graphical analysis, it is concluded that using some specific values of the involved parameters, the reconstructed scalar field potentials are cosmologically viable in both cases.

scholarly journals Tachyonic matter cosmology with exponential and hyperbolic potentials

2017 ◽  
Vol 26 (02) ◽  
pp. 1750012 ◽  
Author(s):  
B. Pourhassan ◽  
J. Naji
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Cosmological Parameters ◽  
Field Potentials ◽  
Exponential Potential ◽  
Frw Universe ◽  
Hyperbolic Cosine ◽  
Special Cases ◽  
Friedmann Robertson Walker ◽  
Type Potential

In this paper, we consider tachyonic matter in spatially flat Friedmann–Robertson–Walker (FRW) universe, and obtain behavior of some important cosmological parameters for two special cases of potentials. First, we assume the exponential potential and then consider hyperbolic cosine type potential. In both cases, we obtain behavior of the Hubble, deceleration and EoS parameters. Comparison with observational data suggest the model with hyperbolic cosine type scalar field potentials has good model to describe universe.

scholarly journals Reconstructing f(R) gravity from a Chaplygin scalar field in de Sitter spacetimes

2018 ◽  
Vol 15 (02) ◽  
pp. 1850027 ◽  
Author(s):  
Heba Sami ◽  
Neo Namane ◽  
Joseph Ntahompagaze ◽  
Maye Elmardi ◽  
Amare Abebe
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Field Model ◽  
Exact Formula ◽  
Chaplygin Gas ◽  
Reconstruction Technique ◽  
Field Potentials ◽  
De Sitter ◽  
Cosmological Expansion ◽  
Lagrangian Densities

We present a reconstruction technique for models of [Formula: see text] gravity from the Chaplygin scalar field in flat de Sitter spacetimes. Exploiting the equivalence between [Formula: see text] gravity and scalar–tensor (ST) theories, and treating the Chaplygin gas (CG) as a scalar field model in a universe without conventional matter forms, the Lagrangian densities for the [Formula: see text] action are derived. Exact [Formula: see text] models and corresponding scalar field potentials are obtained for asymptotically de Sitter spacetimes in early and late cosmological expansion histories. It is shown that the reconstructed [Formula: see text] models all have General Relativity (GR) as a limiting solution.

POWER-LOW EXPANSION IN k-ESSENCE COSMOLOGY

2004 ◽  
Vol 19 (10) ◽  
pp. 761-768 ◽  
Author(s):  
LUIS P. CHIMENTO ◽  
ALEXANDER FEINSTEIN
Keyword(s):  
Gravitational Field ◽  
Scalar Field ◽  
Field Model ◽  
Constant Function ◽  
Field Potentials ◽  
Field Equations ◽  
Large Window ◽  
The Family ◽  
Stable Solutions ◽  
Linear Scalar

We study spatially flat isotropic universes driven by k-essence. It is shown that Friedmann and k-field equations may be analytically integrated for arbitrary k-field potentials during evolution with a constant baryotropic index. It follows that there is an infinite number of dynamically different k-theories with equivalent kinematics of the gravitational field. We show that there is a large "window" of stable solutions, and that the dust-like behavior separates stable from unstable expansion. Restricting to the family of power law solutions, it is argued that the linear scalar field model, with constant function F, is isomorphic to a model with divergent speed of sound and this makes them less suitable for cosmological modeling than the nonlinear k-field solutions we find in this paper.

scholarly journals Nonminimal kinetic coupled gravity: Inflation on the warped DGP brane

2016 ◽  
Vol 31 (10) ◽  
pp. 1650047
Author(s):  
F. Darabi ◽  
A. Parsiya ◽  
K. Atazadeh
Keyword(s):  
Scalar Field ◽  
Coupling Constants ◽  
Kinetic Term ◽  
Field Potentials ◽  
Coupling Constant ◽  
Field Equations ◽  
Einstein Tensor ◽  
Brane Model ◽  
Walker Metric ◽  
Friedmann Robertson Walker

We consider the nonminimally kinetic coupled version of DGP brane model, where the kinetic term of the scalar field is coupled to the metric and Einstein tensor on the brane by a coupling constant [Formula: see text]. We obtain the corresponding field equations, using the Friedmann–Robertson–Walker metric and the perfect fluid, and study the inflationary scenario to confront the numerical analysis of six typical scalar field potentials with the current observational results. We find that among the suggested potentials and coupling constants, subject to the e-folding [Formula: see text], the potentials [Formula: see text], [Formula: see text] and [Formula: see text] provide the best fits with both Planck+WP+highL data and Planck+WP+highL+BICEP2 data.

scholarly journals CHAOS IN CLOSED ISOTROPIC COSMOLOGICAL MODELS WITH STEEP SCALAR FIELD POTENTIAL

1999 ◽  
Vol 08 (06) ◽  
pp. 739-750 ◽  
Author(s):  
A. V. TOPORENSKY
Keyword(s):  
Scalar Field ◽  
Chaotic Dynamics ◽  
Chaotic Behavior ◽  
Field Potential ◽  
Equation Of Motion ◽  
Cosmological Models ◽  
Field Potentials ◽  
Numerical Investigations ◽  
Analytical Studies

The dynamics of closed scalar field FRW cosmological models is studied for several types of exponentially and more than exponentially steep potentials. The parameters of scalar field potentials which allow a chaotic behavior are found from numerical investigations. It is argued that analytical studies of equation of motion at the Euclidean boundary can provide an important information about the properties of chaotic dynamics. Several types of transition from chaotic to regular dynamics are described.

scholarly journals Friedmann inflation in Horava–Lifshitz gravity with a scalar field

2016 ◽  
Vol 31 (09) ◽  
pp. 1650042 ◽  
Author(s):  
Abdel Nasser Tawfik ◽  
Abdel Magied Diab ◽  
Eiman Abou El Dahab
Keyword(s):  
Scalar Field ◽  
Spectral Density ◽  
Equations Of State ◽  
Density Fluctuations ◽  
Regular Pattern ◽  
Field Potentials ◽  
Potential Models ◽  
Friedmann Equations ◽  
Slow Roll ◽  
Cosmic Background

We study Friedmann inflation in general Horava–Lifshitz (HL) gravity with detailed and nondetailed and also without the projectability conditions. Accordingly, we derive the modifications in the Friedmann equations due to single scalar field potentials describing power-law and minimal-supersymmetrically extended inflation. By implementing four types of the equations-of-state characterizing the cosmic background geometry, the dependence of the tensorial and spectral density fluctuations and their ratio on the inflation field is determined. The latter characterizes the time evolution of the inflation field relative to the Hubble parameter. Furthermore, the ratio of tensorial-to-spectral density fluctuations is calculated in dependence on the spectral index. The resulting slow-roll parameters apparently differ from the ones deduced from the standard General Relativity (Friedmann gravity). We also observe that the tensorial-to-spectral density fluctuations continuously decrease when moving from nondetailed HL gravity, to Friedmann gravity, to HL gravity without the projectability, and to detailed HL gravity. This regular pattern is valid for three types of cosmic equations-of-state and different inflation potential models. The results fit well with the recent Planck observations.

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