Observational evidence of dark energy

Dark Energy ◽  
2013 ◽  
pp. 84-108
Author(s):  
Luca Amendola ◽  
Shinji Tsujikawa
Keyword(s):  
Dark Energy ◽  
Observational Evidence

Dark energy model in higher-dimensional FRW universe with respect to generalized entropy of Sharma and Mittal of flat FRW space–time

2019 ◽  
Vol 97 (11) ◽  
pp. 1185-1186 ◽  
Author(s):  
E.C. Gunay Demirel
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
State Parameter ◽  
Space Time ◽  
Observational Evidence ◽  
The State ◽  
Frw Universe ◽  
Generalized Entropy ◽  
Higher Dimensional ◽  
Friedmann Robertson Walker

In this study, we report the state parameter of dark energy in higher dimensional Friedmann–Robertson–Walker (FRW) space–time according to generalized entropy of Sharma and Mittal. In this case we analyze the state parameter of dark energy according to today’s observational evidence.

Dark matter (energy) may be indistinguishable from modified gravity (MOND)

2017 ◽  
Vol 26 (12) ◽  
pp. 1743010 ◽  
Author(s):  
C. Sivaram
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Dark Energy ◽  
Modified Gravity ◽  
Observational Evidence ◽  
Negative Results ◽  
Newtonian Dynamics ◽  
Special Cases ◽  
The Universe ◽  
Matter Energy

For Newtonian dynamics to hold over galactic scales, large amounts of dark matter (DM) are required which would dominate cosmic structures. Accounting for the strong observational evidence that the universe is accelerating requires the presence of an unknown dark energy (DE) component constituting about 70% of the matter. Several ingenious ongoing experiments to detect the DM particles have so far led to negative results. Moreover, the comparable proportions of the DM and DE at the present epoch appear unnatural and not predicted by any theory. For these reasons, alternative ideas like MOND and modification of gravity or general relativity over cosmic scales have been proposed. It is shown in this paper that these alternate ideas may not be easily distinguishable from the usual DM or DE hypotheses. Specific examples are given to illustrate this point that the modified theories are special cases of a generalized DM paradigm.

scholarly journals AGE CONSTRAINTS ON THE COSMIC EQUATION OF STATE

2007 ◽  
Vol 16 (02n03) ◽  
pp. 463-468
Author(s):  
N. PIRES ◽  
J. S. ALCANIZ
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Observational Evidence ◽  
Accelerating Universe ◽  
Observational Constraints ◽  
Energy Component ◽  
Dark Energy Component ◽  
Age Constraints ◽  
Friedmann Robertson Walker ◽  
Age Estimates

A large amount of recent observational evidence strongly suggests that we live in a flat, accelerating universe composed of ≃ 1/3 of matter (barionic + dark) and ≃ 2/3 of an exotic component with large negative pressure, usually called dark energy or "quintessence." In this contribution, we investigate observational constraints on the equation of state of the dark energy from age estimates of galaxy clusters, supernovae observations and CMB measurements. Our results are based on a flat Friedmann–Robertson–Walker (FRW) type models driven by non-relativistic matter plus a smooth dark energy component parametrized by a constant equation of state px = ωωx (ω < 0).

scholarly journals The Influence of Evolving Dark Energy on Cosmology

2005 ◽  
Vol 22 (4) ◽  
pp. 315-325 ◽  
Author(s):  
Luke Barnes ◽  
Matthew J. Francis ◽  
Geraint F. Lewis ◽  
Eric V. Linder
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Constant ◽  
Energy Exchange ◽  
Observational Evidence ◽  
Cosmological Models ◽  
Observational Constraints ◽  
Expansion Of The Universe ◽  
The Universe

AbstractObservational evidence indicating that the expansion of the universe is accelerating has surprised cosmologists in recent years. Cosmological models have sought to explain this acceleration by incorporating ‘dark energy’, of which the traditional cosmological constant is just one possible candidate. Several cosmological models involving an evolving equation of state of the dark energy have been proposed, as well as possible energy exchange to other components, such as dark matter. This paper summarizes the forms of the most prominent models and discusses their implications for cosmology and astrophysics. Finally, this paper examines the current and future observational constraints on the nature of dark energy.

Peculiarity Parameters

1976 ◽  
Vol 32 ◽  
pp. 233-254
Author(s):  
H. M. Maitzen
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Theoretical Work ◽  
Observational Evidence ◽  
Rotator Model ◽  
Peculiar Behaviour ◽  
Field Spectrum ◽  
Oblique Rotator ◽  
Ap Stars ◽  
The Way

Ap stars are peculiar in many aspects. During this century astronomers have been trying to collect data about these and have found a confusing variety of peculiar behaviour even from star to star that Struve stated in 1942 that at least we know that these phenomena are not supernatural. A real push to start deeper theoretical work on Ap stars was given by an additional observational evidence, namely the discovery of magnetic fields on these stars by Babcock (1947). This originated the concept that magnetic fields are the cause for spectroscopic and photometric peculiarities. Great leaps for the astronomical mankind were the Oblique Rotator model by Stibbs (1950) and Deutsch (1954), which by the way provided mathematical tools for the later handling pulsar geometries, anti the discovery of phase coincidence of the extrema of magnetic field, spectrum and photometric variations (e.g. Jarzebowski, 1960).

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