scholarly journals Cosmic evolution in f(T) gravity theory

2020 ◽  
Vol 35 (36) ◽  
pp. 2050296
Author(s):  
Akash Bose ◽  
Subenoy Chakraborty
Keyword(s):  
Gravity Theory ◽  
Proper Choice ◽  
Late Time ◽  
Evolution Of The Universe ◽  
Late Time Acceleration ◽  
Cosmic Evolution ◽  
Emergent Scenario ◽  
Cosmological Solutions ◽  
Modified Formula ◽  
The Universe

The paper deals with cosmology in modified [Formula: see text] gravity theory. With some phenomenological choices for the function [Formula: see text] it is possible to have cosmological solutions describing different phases of the evolution of the Universe for the homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker (FLRW) model. By proper choice of the parameters involved in the function [Formula: see text] and also in the cosmological solutions it is shown that a continuous cosmic evolution starting from the emergent scenario to the present late-time acceleration is possible. Finally thermodynamical analysis of [Formula: see text] gravity is presented.

scholarly journals DARK ENERGY IN PRACTICE

2010 ◽  
Vol 25 (29) ◽  
pp. 5253-5331 ◽  
Author(s):  
DOMENICO SAPONE
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Complete List ◽  
Late Time ◽  
Evolution Of The Universe ◽  
Late Time Acceleration ◽  
Energy Models ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Alternative Theories

In this paper we review a part of the approaches that have been considered to explain the extraordinary discovery of the late time acceleration of the Universe. We discuss the arguments that have led physicists and astronomers to accept dark energy as the current preferable candidate to explain the acceleration. We highlight the problems and the attempts to overcome the difficulties related to such a component. We also consider alternative theories capable of explaining the acceleration of the Universe, such as modification of gravity. We compare the two approaches and point out the observational consequences, reaching the sad but foresightful conclusion that we will not be able to distinguish between a Universe filled by dark energy or a Universe where gravity is different from General Relativity. We review the present observations and discuss the future experiments that will help us to learn more about our Universe. This is not intended to be a complete list of all the dark energy models but this paper should be seen as a review on the phenomena responsible for the acceleration. Moreover, in a landscape of hardly compelling theories, it is an important task to build simple measurable parameters useful for future experiments that will help us to understand more about the evolution of the Universe.

scholarly journals A NOTE ON THE COSMOLOGICAL DYNAMICS IN FINITE-RANGE GRAVITY

2003 ◽  
Vol 12 (04) ◽  
pp. 689-696 ◽  
Author(s):  
M. SAMI
Keyword(s):  
Phase Space ◽  
Gravity Theory ◽  
Accelerated Expansion ◽  
Late Time ◽  
Finite Range ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
Late Time Acceleration ◽  
Isotropic Cosmology ◽  
The Universe

In this note we consider the homogeneous and isotropic cosmology in the finite-range gravity theory recently proposed by Babak and Grishchuk. In this scenario the universe undergoes late time accelerated expansion if both the massive gravitons present in the model are tachyons. We carry out the phase space analysis of the system and show that the late-time acceleration is an attractor of the model.

Continuous cosmic evolution with diffusive barotropic fluid: First-order thermodynamic phase transition

2021 ◽  
Author(s):  
Subhayan Maity ◽  
Subenoy Chakraborty
Keyword(s):  
Phase Transition ◽  
Analytic Continuation ◽  
Late Time ◽  
Barotropic Fluid ◽  
First Order ◽  
Late Time Acceleration ◽  
Friedmann Equations ◽  
Cosmic Evolution ◽  
Emergent Scenario ◽  
Thermodynamic Phase

In the background of homogeneous and isotropic flat FLRW model, a complete cosmic scenario from nonsingular emergent scenario to the present late time acceleration through inflationary era and matter-dominated epoch has been presented in this work with cosmic matter in the form of diffusive barotropic fluid. By proper choices of the diffusion parameter and using Friedmann equations, it is possible to show the transitions: Emergent scenario[Formula: see text]Inflationary era[Formula: see text]matter-dominated phase[Formula: see text]Late time acceleration epoch. In analogy with analytic continuation, it is found that the above evolution will be continuous for suitable values of the parameters involved. Finally, possible first-order thermodynamic phase transition has been analyzed for such cosmic evolution.

Early inflation to late-time acceleration in f(G) model

2016 ◽  
Vol 31 (33) ◽  
pp. 1650187
Author(s):  
Malay Krishna Dutta ◽  
Kaushik Sarkar ◽  
B. Modak
Keyword(s):  
Ideal Fluid ◽  
Deceleration Parameter ◽  
Accelerating Universe ◽  
Late Time ◽  
Evolution Of The Universe ◽  
Late Time Acceleration ◽  
Modified Theory Of Gravity ◽  
Theory Of Gravity ◽  
The Universe ◽  
Modified Theory

We present some solutions in Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime in the modified theory of gravity with a general Gauss–Bonnet (GB) term f(G) and R2 including an ideal fluid. We present evolution of the universe introducing an ansatz without a prior choice of f(G) in one approach, while in other class of model, the solutions are obtained assuming few simple forms of f(G). Some of the solutions show early inflationary expansion, further in one solution the fluctuation of the deceleration parameter q is evident at the end of inflation. In all cases, late-time transition to accelerating universe at redshift z [Formula: see text] 0.7 is realizable.

scholarly journals Chameleon field and the late time acceleration of the Universe

Pramana ◽  
2010 ◽  
Vol 74 (3) ◽  
pp. 481-489 ◽  
Author(s):  
Narayan Banerjee ◽  
Sudipta Das ◽  
Koyel Ganguly
Keyword(s):  
Late Time ◽  
Late Time Acceleration ◽  
Acceleration Of The Universe ◽  
The Universe

MODIFIED GRAVITY THEORY DUE TO POSITIVE AS WELL AS NEGATIVE CURVATURE INDUCED ACCELERATION

2012 ◽  
Vol 21 (02) ◽  
pp. 1250012
Author(s):  
PRIYADARSHI MAJUMDAR
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Negative Curvature ◽  
Gravity Theory ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Negative Power ◽  
Modified Gravity Theory ◽  
Phase Q ◽  
The Universe

We formulate a modified gravity theory that eliminates the need for dark energy and is stable for a Lagrangian containing R, R2 as well as 1/R terms (i.e. nonlinear contributions of the Ricci curvature with a non-analytic model of f(R) at R = 0) without considering any matter-dominated era. The terms with positive powers (1, 2) of the curvature support the inflationary epoch while the terms with negative power (-1) serves as effective dark energy, supporting current cosmic acceleration. We present a few analytical solutions of evolution equation for the deceleration parameter q as a function of Hubble parameter H and time t; specially in one solution, the universe evolves continuously from q = 1 (a radiation-dominated epoch) to q = -1/2 (dark-energy-dominated late-time accelerating phase) when the universe is sufficiently old. The solution is supported by numerical results. The transition from the decelerated (q > 0) to the accelerated phase (q < 0) of expansion takes place smoothly without having to resort to a study of asymptotic behavior.

scholarly journals Dirac Field as a Source of the Inflation in2+1Dimensional Teleparallel Gravity

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Ganim Gecim ◽  
Yusuf Sucu
Keyword(s):  
Early Time ◽  
Teleparallel Gravity ◽  
Noether Symmetry ◽  
Dirac Field ◽  
Late Time ◽  
Late Time Acceleration ◽  
Symmetry Approach ◽  
Gauge Term ◽  
Acceleration Of The Universe ◽  
The Universe

In this paper, we study early-time inflation and late-time acceleration of the universe by nonminimally coupling the Dirac field with torsion in the spatially flat Friedman-Robertson-Walker (FRW) cosmological model background. The results obtained by the Noether symmetry approach with and without a gauge term are compared. Additionally, we compare these results with that of the3+1dimensional teleparallel gravity under Noether symmetry approach. And we see that the study explains early-time inflation and late-time acceleration of the universe.

scholarly journals Dynamics of two-scalar-field cosmological models beyond the exponential potential

2017 ◽  
Vol 26 (14) ◽  
pp. 1750164 ◽  
Author(s):  
Yu Li
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Cosmological Models ◽  
The Other ◽  
Late Time ◽  
Exponential Potential ◽  
Multiple Attractors ◽  
Evolution Of The Universe ◽  
The Universe

In this paper, we discuss the dynamics of two- scalar-field cosmological models. Unlike in the situation of exponential potential, we find that there are late-time attractors in which one scalar field dominates the energy density of universe and the other one decay. We also discuss the possibility of multiple attractors model which is useful to realize the evolution of the universe from a scaling era to recent acceleration era. We also give the conditions of the existence of multiple attractors.

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