指数模型的重力通货膨胀
76 浏览量
2020-04-09
19:39:48
上传
评论
收藏 1.72MB PDF 举报
Research Article
Inflation in 𝑓(𝑅,𝜙) Gravity with Exponential Model
Farzana Kousar, Rabia Saleem, and M. Zubair
Department of Mathematics, COMSATS University Islamabad, Lahore-Campus, Pakistan
Correspondence should be addressed to M. Zubair; mzubairkk@gmail.com
Received 12 June 2018; Revised 21 August 2018; Accepted 12 September 2018; Published 16 December 2018
A
cad
emic Editor: Torsten Asselmeyer-Maluga
Copyright © 2018 Farzana Kousar et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e
publication of this article was funded by SCOAP
3
.
We are taking action of ()gravity with a nonminimal coupling to a massive inaton eld. A (,)model is chosen which leads
to the scalar-tensor theory which can be transformed to Einstein frame by conformal transformation. To avoid the vagueness of the
frame dependence, we evaluate the exact analytical solutions for inationary era in Jordan frame and nd a condition for graceful
exit from ination. Furthermore, we calculate the perturbed parameters (i.e., number of e-folds, slow-roll parameters, scalar and
tensor power spectra, corresponding spectral indices, and tensor to scalar ratio). It is showed that the tensor power spectra lead to
blue tilt for this model. e trajectories of the perturbed parameters are plotted to compare the results with recent observations.
1. Introduction
e late-time cosmic acceleration was discovered in 1998
[1, 2], based on the observations of type Ia supernovae (SN
Ia) that opened up a new door of research in the eld of
cosmology. e main ingredient of this acceleration, named
as dark energy (DE) [3], has been still a paradigm in spite
of tremendous eorts to understand its origin over the last
decade [4, 5]. Dark energy is dierent from ordinary matter in
the respect that it has huge negative pressure whose equation
of state (EoS) is close to −1. Independent observational data
like SN Ia [6, 7], cosmic microwave background radiation
(CMBR) [8, 9], and baryon acoustic oscillations (BAO) [10–
12] proved that about 70% of the energy density content of the
recent universe comprises DE.
Currently, there are various approaches to construct the
models for the explanation of the behavior of DE. One way
is to modify the dynamical eld equations by taking negative
pressure in the form of energy momentum tensor
𝜇]
.is
classofmodelsincludesination[13],quintessence[14,15],
k-essence [16, 17], and perfect uid models. e perfect uid
models are solved with the combination of EoS like Chaplygin
gas model and the generalization of this model [18, 19]. On
the basis of particle physics, there have been several eorts to
nd the scalar eld models for the explanation of DE [20–22].
e alternative way for the construction of DE model is to
modify the “Einstein-Hilbert action” to attain the modied
gravity theories like ()gravity, ()(where is torsion
scalar) gravity, (,)and Gauss-Bonnet gravity [23–31].
e compelling research phenomena of “cosmological
ination” are introduced by Guth (1981) [32]. In hot big-
bang (HBB) theory, ination is a notion implemented on a
very initial cosmic stage of expansion. e scale of ination
is assumed to be long enough since over and the standard
evolution is rebuilt to hold the prominent triumphs, such as
CMBR and nucleosynthesis. In spite of all of its successes,
there are some puzzles with HBB theory, which generate
ination [33].
e “atness issue” [34]=1on the time scale, where
=/
𝑐
,
𝑐
being critical density. e curvature term,
()
2
(,is the scale factor and the Hubble parameter)
in standard big-bang model, decreases with respect to time
lead to ()varying from unity. However, recent observations
suggested that the value of ()is closed to unity, thus
it must be same in the early-time such that its value is
|(
𝑃𝑙
)|<O(10
−64
)at Planck time while during nucleosyn-
thesis |(
𝑛𝑢𝑐𝑙𝑒𝑜
)| < O(10
−16
). e dierence in numeric
values suggests that initial conditions should be ne-tuned.
An inappropriate choice generates a cosmos, which either
soon expands before the formation of structure or quickly
collapses.
Hindawi
Advances in High Energy Physics
Volume 2018, Article ID 3085761, 10 pages
https://doi.org/10.1155/2018/3085761
剩余10页未读，继续阅读
资源评论
