scholarly journals Cosmic expansion and growth histories in Galileon scalar-tensor models of dark energy

2010 ◽  
Vol 81 (10) ◽  
Author(s):  
Tsutomu Kobayashi
Keyword(s):  
Dark Energy ◽  
Cosmic Expansion ◽  
Tensor Models

Ghost dark energy in Rastall theory

2021 ◽  
pp. 2150090
Author(s):  
E. E. Kangal ◽  
M. Salti ◽  
O. Aydogdu
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Text Analysis ◽  
Functional Form ◽  
Expansion Rate ◽  
Dark Energy Density ◽  
Cosmic Expansion ◽  
Astrophysical Data ◽  
Ghost Dark Energy ◽  
History Of

Making use of the generalized form of the Ghost dark energy density, which has the functional form [Formula: see text] where [Formula: see text] represents the Hubble expanding rate, the present accelerated enlargement behavior of the cosmos is investigated from the Rastall theory perspective. After finding a relation for the Hubble cosmic expansion rate, we consider recent cosmology-independent measurements calculated for the expansion history of the cosmos to fit the model via the [Formula: see text]-analysis. Moreover, we discuss the cosmographic properties of the model with the help of some cosmological quantities. We show that our model is stable and consistent with the recent astrophysical data. Also, for our model, we investigate cosmological interpretations of thermodynamics.

scholarly journals A Topological Magueijo-Smolin Varying Speed of Light Theory, the Accelerated Cosmic Expansion and the Dark Energy of Pure Gravity

2014 ◽  
Vol 05 (12) ◽  
pp. 1780-1790 ◽  
Author(s):  
Mohamed Salah El Naschie ◽  
Leila Marek-Crnjac ◽  
Mohamed Atef Helal ◽  
Ji-Huan He
Keyword(s):  
Dark Energy ◽  
Speed Of Light ◽  
Cosmic Expansion ◽  
Pure Gravity ◽  
Light Theory

THE IMPRINT OF DARK ENERGY

2004 ◽  
Vol 19 (13n16) ◽  
pp. 1063-1070 ◽  
Author(s):  
ROBERT CALDWELL
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmic Microwave Background ◽  
Cosmological Constant ◽  
Negative Pressure ◽  
Inhomogeneous Field ◽  
Time Varying ◽  
Microwave Background ◽  
Cosmic Expansion ◽  
Cosmological Observations

Diverse cosmological observations indicate the existence of dark energy, comprising ~ 70% of the total cosmic energy density and driving the accelerated cosmic expansion. Possible explanations for the dark energy include a cosmological constant and quintessence — a time-varying, inhomogeneous field with negative pressure. In this article we summarize how the dark energy imprints features on the cosmic microwave background. Observation of these features could be useful in discriminating amongst various theories, and could reveal clues as to the nature of the dark energy.

scholarly journals The WiggleZ Dark Energy Survey: measuring the cosmic expansion history using the Alcock-Paczynski test and distant supernovae

2011 ◽  
Vol 418 (3) ◽  
pp. 1725-1735 ◽  
Author(s):  
Chris Blake ◽  
Karl Glazebrook ◽  
Tamara M. Davis ◽  
Sarah Brough ◽  
Matthew Colless ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmic Expansion ◽  
Dark Energy Survey ◽  
Energy Survey ◽  
Cosmic Expansion History

scholarly journals Study of growth matter index and cosmic implications in dynamical Chern–Simons modified gravity

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Saba Qummer ◽  
Amir Sharif
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Growth Index ◽  
Simons Theory ◽  
Cosmic Expansion ◽  
Acceleration Of The Universe ◽  
Expansion Of The Universe ◽  
Chern Simons ◽  
The Universe

AbstractIn the framework of dynamical Chern–Simons theory of gravity, we study the recent cosmic expansion with acceleration of the universe. We take interacting scenario of dark energy and dark matter with three cutoffs like Granda–Oliveros, higher order derivative of Hubble parameter and generalized holographic dark energy model. In the flat Friedmann–Robertson–Walker universe, well-known cosmological parameters have been calculated. We study the perturbation of matter density growth, growth factor and growth index behavior for the underlying framework. The cosmological parameters like equation of state parameter, deceleration parameter, and stability of each model are discussed. The outcomes of these models represent the cosmic expansion of the universe with acceleration.

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 Remarks on generalized scalar-tensor models of dark energy

2009 ◽  
Vol 80 (6) ◽  
Author(s):  
M. Alimohammadi ◽  
H. Behnamian
Keyword(s):  
Dark Energy ◽  
Tensor Models

scholarly journals Are the “Physically Bound Systems” beyond the Cosmological Expansion Effect? (A provocative musing on the given theme)

2013 ◽  
Vol 9 (S304) ◽  
pp. 391-394
Author(s):  
Haik A. Harutyunian
Keyword(s):  
Dark Energy ◽  
Energy Exchange ◽  
Ordinary Matter ◽  
Cosmic Expansion ◽  
Cluster Of Galaxies ◽  
Cosmological Expansion ◽  
Ejection Mechanism ◽  
The Given ◽  
Expansion Effect ◽  
Hubble Time

AbstractInfluence of the dark energy at small scales is considered. Interaction and energy exchange between ordinary matter and dark energy is proposed as a working hypothesis. Some observational facts are put into the base of this consideration: the large rate of lunar retreat and the acceleration of cosmic expansion which proves the energy exchange between ordinary matter and dark energy. If the possibility of the space and matter expansion at the scales under consideration is accepted one can show that the dark energy transformed into the object's potential energy is enough to generate cluster of galaxies over the Hubble time due to matter ejection mechanism.

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