scholarly journals Magnetized dark energy and the late time acceleration

2012 ◽  
Vol 127 (10) ◽  
Author(s):  
A. K. Yadav ◽  
F. Rahaman ◽  
S. Ray ◽  
G. K. Goswami
Keyword(s):  
Dark Energy ◽  
Late Time ◽  
Late Time Acceleration

scholarly journals A COSMOLOGICAL MODEL WITH FERMIONIC FIELD

2010 ◽  
Vol 25 (13) ◽  
pp. 2735-2746 ◽  
Author(s):  
R. RAKHI ◽  
G. V. VIJAYAGOVINDAN ◽  
K. INDULEKHA
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
The Self ◽  
Late Time ◽  
Fermionic Field ◽  
Energy Field ◽  
Late Time Acceleration ◽  
Higher Order Terms ◽  
Interaction Term ◽  
M Theory

In this work, a cosmological model inspired by string/M-theory with fermionic field is taken into consideration. Here it is investigated whether the introduction of a non-Dirac fermionic field — characterized by an interaction term — affects the cosmological evolution. The self-interaction potential is considered as a combination of the scalar and pseudoscalar invariants. It is observed that the fermionic field under consideration behaves like an inflation field for the early universe and later on, as a dark energy field. The late time acceleration becomes more prominent by the addition of the interaction term. There is a slight decrease for the inflation peak as well as for the energy density. We see that the addition of higher-order terms to the fermionic part of Lagrangian does not significantly change either the inflation or the late time acceleration behavior.

scholarly journals Dark energy in modified Gauss-Bonnet gravity: Late-time acceleration and the hierarchy problem

2006 ◽  
Vol 73 (8) ◽  
Author(s):  
Guido Cognola ◽  
Emilio Elizalde ◽  
Shin’ichi Nojiri ◽  
Sergei D. Odintsov ◽  
Sergio Zerbini
Keyword(s):  
Dark Energy ◽  
Late Time ◽  
Hierarchy Problem ◽  
Bonnet Gravity ◽  
Late Time Acceleration

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 POWER-LAWS f(R) THEORIES ARE COSMOLOGICALLY UNACCEPTABLE

2007 ◽  
Vol 16 (10) ◽  
pp. 1555-1561 ◽  
Author(s):  
LUCA AMENDOLA ◽  
DAVID POLARSKI ◽  
SHINJI TSUJIKAWA
Keyword(s):  
Dark Energy ◽  
Recent Work ◽  
Modified Gravity ◽  
Cosmic Time ◽  
Power Laws ◽  
Scale Factor ◽  
Late Time ◽  
Cosmic Expansion ◽  
Late Time Acceleration ◽  
Energy Models

In a recent paper,1 we have shown that f(R) = R + μRn modified gravity dark energy models are not cosmologically viable because during the matter era that precedes the accelerated stage the cosmic expansion is given by a ~ t1/2 rather than a ~ t2/3, where a is a scale factor and t is the cosmic time. A recent work by Capozziello et al.2 criticized our results presenting some apparent counter-examples to our claim in f(R) = μRn models. We show here that those particular Rn models can produce an expansion as a ~ t2/3 but this does not connect to a late-time acceleration. Hence, though acceptable f(R) dark energy models might exist, the Rn models presented in Capozziello et al. are not cosmologically viable, confirming our previous results in Ref. 1.

scholarly journals Invisible QCD as Dark Energy

Universe ◽  
2020 ◽  
Vol 6 (6) ◽  
pp. 75
Author(s):  
Andrea Addazi ◽  
Stephon Alexander ◽  
Antonino Marcianò
Keyword(s):  
Dark Energy ◽  
Stability Analysis ◽  
Equation Of State ◽  
Quantum Chromodynamics ◽  
Early Universe ◽  
Negative Pressure ◽  
Late Time ◽  
Late Time Acceleration ◽  
Acceleration Of The Universe ◽  
The Universe

We account for the late time acceleration of the Universe by extending the Quantum Chromodynamics (QCD) color to a S U ( 3 ) invisible sector (IQCD). If the Invisible Chiral symmetry is broken in the early universe, a condensate of dark pions (dpions) and dark gluons (dgluons) forms. The condensate naturally forms due to strong dynamics similar to the Nambu–Jona-Lasinio mechanism. As the Universe evolves from early times to present times the interaction energy between the dgluon and dpion condensate dominates with a negative pressure equation of state and causes late time acceleration. We conclude with a stability analysis of the coupled perturbations of the dark pions and dark gluons.

scholarly journals Mimetic F(R) gravity: Inflation, dark energy and bounce

2014 ◽  
Vol 29 (40) ◽  
pp. 1450211 ◽  
Author(s):  
Shin'ichi Nojiri ◽  
Sergei D. Odintsov
Keyword(s):  
Dark Energy ◽  
Lagrange Multiplier ◽  
Scalar Potential ◽  
Early Time ◽  
Late Time ◽  
Late Time Acceleration ◽  
Observable Data ◽  
Universe Evolution

We propose the mimetic F(R) theory and investigate the early-time and late-time acceleration in such theory. It is demonstrated that inflation consistent with observable data may be realized in such theory. The reconstruction of realistic ΛCDM era is also possible as well as the unification of early-time inflation with late-time acceleration or bounce universe. It is stressed that specific universe evolution is governed by mimetic F(R) theory which is different from convenient F(R) gravity. The corresponding examples are presented. Mimetic F(R) gravity is generalized by the addition of the scalar potential in the formulation of convenient F(R) gravity with specific Lagrange multiplier constraint. It is demonstrated that such theory may admit the arbitrary universe evolution via the corresponding choice of the scalar potential and/or function F(R).

scholarly journals Quintessential inflation: A unified scenario of inflation and dark energy

2018 ◽  
Vol 168 ◽  
pp. 04007 ◽  
Author(s):  
Wali Hossain
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Scalar Fields ◽  
Late Time ◽  
Planck Data ◽  
Inflaton Field ◽  
Late Time Acceleration ◽  
Quintessence Field

Quintessential inflation unifies inflation and late time acceleration by a single scalar field. Such a scenario, with canonical and non-canonical scalar fields, has been discussed. The scalar field behaves as an inflaton field during inflation and as a quintessence field during late time. Also the predictions of the models has been compared with the recent Planck data.

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