scholarly journals BIG RIP AND LITTLE RIP SOLUTIONS IN SCALAR MODEL WITH KINETIC AND GAUSS–BONNET COUPLINGS

2012 ◽  
Vol 21 (01) ◽  
pp. 1250002 ◽  
Author(s):  
L. N. GRANDA ◽  
E. LOAIZA
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Hubble Parameter ◽  
Field Model ◽  
Kinetic Term ◽  
Late Time ◽  
Scalar Model ◽  
Big Rip ◽  
Specific Choice ◽  
Cosmological Solutions

Late time cosmological solutions for scalar field model with kinetic and Gauss–Bonnet couplings are considered. The quintom scenario is realized with and without Big Rip singularity. We find that under specific choice of the Gauss–Bonnet coupling, the model considerably simplifies, giving rise to solutions where the kinetic term is proportional to the square of the Hubble parameter. This allows to reconstruct the model for a suitable cosmological evolution. We considered a solution that matches the observed behavior of the equation of state, while Big Rip singularity may be present or absent, depending on the parameters of the solution. Evolutionary scenarios known as Little Rip, have also been considered.

scholarly journals Light of Planck-2015 on Noncanonical Inflation

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Kh. Saaidi ◽  
A. Mohammadi ◽  
T. Golanbari
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Power Law ◽  
Hubble Parameter ◽  
Field Model ◽  
Kinetic Term ◽  
Inflationary Scenario ◽  
Slow Roll ◽  
Power Law Function ◽  
Free Parameters

Slow-roll inflationary scenario is considered in noncanonical scalar field model supposing a power-law function for kinetic term and using two formalisms. In the first approach, the potential is picked out as a power-law function, that is, the most common approach in studying inflation. Hamilton-Jacobi approach is selected as the second formalism, so that the Hubble parameter is introduced as a function of scalar field instead of the potential. Employing the last observational data, the free parameters of the model are constrained, and the predicted form of the potential and attractor behavior of the model are studied in detail.

scholarly journals INFLATION IS PERHAPS THE GENERIC FEATURE OF PHANTOM FIELD, NOT THE BIG-RIP

2007 ◽  
Vol 22 (07) ◽  
pp. 1301-1315 ◽  
Author(s):  
ABHIK KUMAR SANYAL
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Hubble Parameter ◽  
State Parameter ◽  
Simple Method ◽  
Dynamical State ◽  
Phantom Field ◽  
Big Rip

A class of solutions for phantom field corresponding to a generalized k-essence Lagrangian has been presented, employing a simple method which provides the scope to explore many such. All the solutions having dynamical state parameter are found to touch the magic line w = -1 asymptotically. The solutions with constant equation of state can represent phantom, quitessence or an ordinary scalar field cosmologies depending on the choice of a couple of parameters of the theory. For w ≈ -1, quintessence and phantom models are indistinguishable through the Hubble parameter. Finally, it appears that inflation rather than big-rip is the generic feature of phantom cosmology.

Bouncing scenario in Brans–Dicke theory

2020 ◽  
Vol 17 (04) ◽  
pp. 2050056
Author(s):  
Sunil Kumar Tripathy ◽  
Subingya Pandey ◽  
Alaka Priyadarsini Sendha ◽  
Dipanjali Behera
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Linear Equation ◽  
Scale Factor ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Dark Fluid

A bouncing scenario is studied in the framework of generalized Brans–Dicke theory. In order to have a dark energy (DE) driven late time cosmic acceleration, we have considered a unified dark fluid simulated by a linear equation of state (EoS). The evolutionary behavior of the DE equation of parameter derived from the unified dark fluid has been discussed. The effect of the bouncing scale factor on the Brans–Dicke parameter, self-interacting potential and the Brans–Dicke scalar field is investigated.

scholarly journals Chameleon field dynamics during inflation

2018 ◽  
Vol 27 (04) ◽  
pp. 1850041 ◽  
Author(s):  
Nasim Saba ◽  
Mehrdad Farhoudi
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
State Parameter ◽  
Big Bang ◽  
Late Time ◽  
Inflationary Model ◽  
Slow Roll ◽  
Equation Of State Parameter ◽  
The Common ◽  
The Universe

By studying the chameleon model during inflation, we investigate whether it can be a successful inflationary model, wherein we employ the common typical potential usually used in the literature. Thus, in the context of the slow-roll approximations, we obtain the e-folding number for the model to verify the ability of resolving the problems of standard big bang cosmology. Meanwhile, we apply the constraints on the form of the chosen potential and also on the equation of state parameter coupled to the scalar field. However, the results of the present analysis show that there is not much chance of having the chameleonic inflation. Hence, we suggest that if through some mechanism the chameleon model can be reduced to the standard inflationary model, then it may cover the whole era of the universe from the inflation up to the late time.

scholarly journals Study of Homogeneous and Isotropic Universe in f(R,Tφ) Gravity

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
M. Sharif ◽  
Aisha Siddiqa
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Hubble Parameter ◽  
State Parameter ◽  
Universe Model ◽  
Effective Equation ◽  
Isotropic Universe ◽  
First Order ◽  
Equation Of State Parameter

This paper is devoted to study the cosmological behavior of homogeneous and isotropic universe model in the context of f(R,Tφ) gravity, where φ is the scalar field. For this purpose, we follow the first-order formalism defined by H=W(φ). We evaluate Hubble parameter, effective equation of state parameter (ωeff), deceleration parameter, and potential of scalar field for three different values of W(φ). We obtain phantom era in some cases for the early times. It is found that exponential expression of W(φ) yields ωeff independent of time for flat universe and independent of model parameter otherwise. It is concluded that our model corresponds to ΛCDM for both initial and late times.

scholarly journals ON BIG RIP SINGULARITIES

2004 ◽  
Vol 19 (33) ◽  
pp. 2479-2484 ◽  
Author(s):  
L. P. CHIMENTO ◽  
RUTH LAZKOZ
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Energy Condition ◽  
Scale Factor ◽  
Late Time ◽  
Strong Energy Condition ◽  
Phantom Field ◽  
Big Rip ◽  
Strong Energy ◽  
Time Singularities

Here we discuss big rip singularities occurring in typical phantom models by violation of the weak energy condition. After that, we compare them with future late-time singularities arising in models where the scale factor ends in a constant value and there is no violation of the strong energy condition. In phantom models the equation of state is well defined along the whole evolution, even at the big rip. However, both the pressure and the energy density of the phantom field diverge. In contrast, in the second kind of model the equation of state is not defined at the big rip because the pressure bursts at a finite value of the energy density.

scholarly journals Unification of inflation and dark energyà laquintessential inflation

2015 ◽  
Vol 24 (05) ◽  
pp. 1530014 ◽  
Author(s):  
Md. Wali Hossain ◽  
R. Myrzakulov ◽  
M. Sami ◽  
Emmanuel N. Saridakis
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
High Energy ◽  
Kinetic Term ◽  
Late Time ◽  
Time Behavior ◽  
History Of ◽  
Field Dynamic ◽  
Relic Gravitational Waves ◽  
Radiative Regime

This pedagogical review is devoted to quintessential inflation, which refers to unification of inflation and dark energy using a single scalar field. We present a brief but concise description of the concepts needed to join the two ends, which include discussion on scalar field dynamic, conformal coupling, instant preheating and relic gravitational waves. Models of quintessential inflation broadly fall into two classes, depending upon the early and late time behavior of the field potential. In the first type we include models in which the field potential is steep for most of the history of the universe but turn shallow at late times, whereas in the second type the potential is shallow at early times followed by a steep behavior thereafter. In models of the first category inflation can be realized by invoking high-energy brane-induced damping, which is needed to facilitate slow roll along a steep potential. In models of second type one may invoke a nonminimal coupling of the scalar field with massive neutrino matter, which might induce a minimum in the potential at late times as neutrinos turn nonrelativistic. In this category we review a class of models with noncanonical kinetic term in the Lagrangian, which can comply with recent B mode polarization measurements. The scenario under consideration is distinguished by the presence of a kinetic phase, which precedes the radiative regime, giving rise to blue spectrum of gravity waves generated during inflation. We highlight the generic features of quintessential inflation and also discuss on issues related to Lyth bound.

scholarly journals Smooth Crossing ofwΛ=−1Line in a Single Scalar Field Model

2009 ◽  
Vol 2009 ◽  
pp. 1-14 ◽  
Author(s):  
Abhik Kumar Sanyal
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Cosmological Model ◽  
Simple Form ◽  
Cold Dark Matter ◽  
Field Model ◽  
Late Time ◽  
Transient Phenomenon ◽  
Phantom Divide ◽  
Phantom Divide Line

Smooth double crossing of the phantom divide linewΛ=−1has been found possible with a single minimally coupled scalar field for the most simple form of generalizedk-essence cosmological model, in the presence of background cold dark matter. Such crossing is a sufficiently late time transient phenomenon and does not have any pathological behaviour.

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