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We study $F(R)$ modified gravity models which are capable of driving the accelerating epoch of the Universe at the present time whilst not destroying the standard Big Bang and inflationary cosmology. Recent studies have shown that a weak…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-13 Stephen Appleby , Richard Battye , Alexei Starobinsky

An oscillating universe cycles through a series of expansions and contractions. We propose a model in which ``phantom'' energy with a supernegative pressure ($p < - \rho$) grows rapidly and dominates the late-time expanding phase. The…

Astrophysics · Physics 2008-03-29 Katherine Freese , Matthew G. Brown , William H. Kinney

In this work we study classical bouncing solutions in the context of $f({\sf R},{\sf T})={\sf R}+h({\sf T})$ gravity in a flat {\sf FLRW} background using a perfect fluid as the only matter content. Our investigation is based on introducing…

General Relativity and Quantum Cosmology · Physics 2018-06-05 Hamid Shabani , Amir Hadi Ziaie

We investigate a bounce realization in the framework of higher order curvature in $ f(R,T) $ modified theory of gravity. We perform a detailed analysis of the cosmological parameters to explain the contraction phase, the bounce phase, and…

General Relativity and Quantum Cosmology · Physics 2023-07-19 J. K. Singh , Shaily , Akanksha Singh , Aroonkumar Beesham , Hamid Shabani

In this paper, we carry out a study of viable cosmological models in $f(R)$-gravity at the background level. We use observable parameters like $\Omega$ and $\gamma$ to form autonomous system of equations and show that the models under…

Cosmology and Nongalactic Astrophysics · Physics 2010-05-28 Amna Ali , Radouane Gannouji , M. Sami , Anjan A. Sen

The basic aim of this manuscript is to investigate the cosmological solutions in the context of the modified $f(R, T)$ theory of gravity, where $R$ is the Ricci scalar and $T$ is the trace of the energy-momentum tensor. For our current…

General Relativity and Quantum Cosmology · Physics 2024-03-26 Adnan Malik , Tayyaba Naz , Aimen Rauf , M. Farasat Shamir , Z. Yousaf

Within the limits of the present cosmological observations in f(R,T) gravity theory, we have analyzed a spherically symmetric space-time in 5D setting. The field equations have been carefully studied considering reasonable cosmological…

General Relativity and Quantum Cosmology · Physics 2020-10-28 Pheiroijam Suranjoy Singh , Kangujam Priyokumar Singh

The paper deals with $f(R)$ gravity theory in the background of inhomogeneous FLRW--type space time model. With proper choice of the inhomogeneous metric function it is possible to have an emergent scenario for the $f(R)$--cosmology.…

General Relativity and Quantum Cosmology · Physics 2018-11-14 Dipanjana Das , Sourav Dutta , Subenoy Chakraborty

In this paper we present the techniques for computing cosmological bounces in polynomial $f(R)$ theories, whose order is more than two, for spatially flat FLRW spacetime. In these cases the conformally connected Einstein frame shows up…

General Relativity and Quantum Cosmology · Physics 2016-02-17 Kaushik Bhattacharya , Saikat Chakrabarty

The four-dimensional Friedman flat universe, filled with an ideal fluid with a linear (oscillating) inhomogeneous equation of state (EoS) depending on time, is studied. The equations of motion are solved. It is shown that in some cases…

General Relativity and Quantum Cosmology · Physics 2008-11-26 I. Brevik , O. G. Gorbunova , A. V. Timoshkin

We study the dynamics of homogeneous isotropic FRW cosmologies with positive spatial curvature in $f(R)$-gravity, paying special attention to the existence of Einstein static models and only study forms of $f(R)=R^n$ for which these static…

General Relativity and Quantum Cosmology · Physics 2009-04-17 Naureen Goheer , Rituparno Goswami , Peter K. S. Dunsby

It is shown that F(R)-modified gravitational theories lead to curvature oscillations in astrophysical systems with rising energy density. The frequency and the amplitude of such oscillations could be very high and would lead to noticeable…

General Relativity and Quantum Cosmology · Physics 2015-06-12 E. V. Arbuzova , A. D. Dolgov , L. Reverberi

An oscillating universe cycles through a series of expansions and contractions. We propose a model in which ``phantom'' energy with $p < -\rho$ grows rapidly and dominates the late-time expanding phase. The universe's energy density is so…

Astrophysics · Physics 2014-10-13 Matthew G. Brown , Katherine Freese , William H. Kinney

We have investigated the evolution of a homogeneous isotropic background of the Universe and inhomogeneous subhorizon matter density perturbations in viable $f(R)$ models of present dark energy and cosmic acceleration analytically and…

Cosmology and Nongalactic Astrophysics · Physics 2011-08-05 Hayato Motohashi , Alexei A. Starobinsky , Jun'ichi Yokoyama

We consider a dynamic scenario for characterizing the late Universe evolution, aiming to mitigate the Hubble tension. Specifically, we consider a metric $f(R)$ gravity in the Jordan frame which is implemented to the dynamics of a flat…

General Relativity and Quantum Cosmology · Physics 2024-08-06 Giovanni Montani , Nakia Carlevaro , Mariaveronica De Angelis

We investigate the cosmic dynamics of Rastall gravity in non-flat Friedmann-Robertson-Walker (FRW) space-time with barotropic fluid. In this context, we are concerned about the class of model satisfying the affine equation of state. We…

General Relativity and Quantum Cosmology · Physics 2022-07-27 Ashutosh Singh , Gyan Prakash Singh , Anirudh Pradhan

We investigate de Sitter solutions in non-local gravity as well as in non-local gravity with Lagrange constraint multiplier. We examine a condition to avoid a ghost and discuss a screening scenario for a cosmological constant in de Sitter…

High Energy Physics - Theory · Physics 2015-05-27 Kazuharu Bamba , Shin'ichi Nojiri , Sergei D. Odintsov , Misao Sasaki

In this work, we study the possibility of finite-time future cosmological singularities appearing in $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of the stress-energy tensor. We present the theory in both the…

General Relativity and Quantum Cosmology · Physics 2022-05-10 Tiago B. Gonçalves , João Luís Rosa , Francisco S. N. Lobo

We investigate the cosmological evolution in a new modified teleparallel theory, called $f(T,B)$ gravity, which is formulated by connecting both $f(T)$ and $f(R)$ theories with a boundary term $B$. Here, $T$ is the torsion scalar in…

General Physics · Physics 2018-11-14 M. Zubair , Saira Waheed , M. Atif Fayyaz , Iftikhar Ahmad

We consider perturbative modifications of the Friedmann equations in terms of energy density corresponding to modified theories of gravity proposed as an alternative route to comply with the observed accelerated expansion of the universe.…

General Relativity and Quantum Cosmology · Physics 2015-05-13 L. Fernández-Jambrina , R. Lazkoz