Cosmologies with a general non-canonical scalar field

Abstract

We generally investigate the scalar field model with the lagrangian L = F (X) − V (φ), which we call it General Non-Canonical Scalar Field Model. We find that it is a special square potential(with a negative minimum) that drives the linear field solution(φ = φ 0 t) while in K-essence model(with the lagrangianthe potential should be taken as an inverse square form. Hence their cosmological evolution are totally different. We further find that this linear field solutions are highly degenerate, and their cosmological evolutions are actually equivalent to the divergent model where its sound speed diverges. We also study the stability of the linear field solution. With a simple form of F (X) = 1 − √ 1 − 2X we indicate that our model may be considered as a unified model of dark matter and dark energy.Finally we study the case when the baryotropic index γ is constant. It shows that, unlike the K-essence, the detailed form of F (X) depends on the potential V (φ). We analyze the stability of this constant γ 0 solution and find that they are stable for γ 0 ≤ 1. Finally we simply consider the constant c 2 s case and get an exact solution for F (X).

Study of non-canonical scalar field model using various parametrizations of dark energy equation of state

“…Unnikrishnan et al [57] have showed that for such models, the slow-roll conditions can be more easily satisfied compared to the canonical case. The non-canonical scalar field models are also found to be able to generate inflation in the early epoch [45,[47][48][49][50][51][52][53][54][55][56][57][58][59]. These attractive features of a noncanonical scalar field motivated us to study the features of this model in the context of dark energy.…”

“…In case of the phantom field, the sign of its kinetic term "X" is opposite compared to the action for a canonical scalar field. The Lagrangian density for a general non-canonical scalar field is given by [59] …”

“…In the non-canonical scalar field models, the kinetic part of the scalar field is modified and it has been found that an accelerated expansion can be achieved through these modifications. Originally, Armendariz-Picon et al [45,46] proposed this scenario to explain inflation at high energies where the non-canonical scalar field efficiently plays the role of inflaton (for review on this topic, see [45,[47][48][49][50][51][52][53][54][55][56][57][58][59]). Later, Chiba et al [13] introduced this scenario for dark energy models.…”

How the scalar field of unified dark matter models can cluster

“…Moreover, for these models, we can use Lagrangians with a non-canonical kinetic term, namely a term which is an arbitrary function of the square of the time derivative of the scalar field, in the homogeneous and isotropic background. These models are known as "k-essence models" [3,4,5,6,7,8] (see also [9,10,11,12,13,14]) and have been inspired by earlier studies of k-inflation [15] [16] (a complete list of dark energy models can be found in the review [17]). …”

Generalized second law of thermodynamics for non-canonical scalar field model with corrected-entropy

“…However, for most of the dark energy models the analysis is carried out for canonical scalar fields. But there is another class of scalar field models, viz, non-canonical scalar field models which have also been considered as a candidate for dark energy (for details see [11][12][13] and the references there in). This class of models has also been found to be a very good candidate for dark energy and could provide solution to a number of cosmological problems.…”