Observational Evidence of Dark Energy at the Background Level

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Andronikos Paliathanasis ◽  
Genly Leon ◽  
Wompherdeiki Khyllep ◽  
Jibitesh Dutta ◽  
Supriya Pan

AbstractWe consider a cosmological scenario endowed with an interaction between the universe’s dark components – dark matter and dark energy. Specifically, we assume the dark matter component to be a pressure-less fluid, while the dark energy component is a quintessence scalar field with Lagrangian function modified by the quadratic Generalized Uncertainty Principle. The latter modification introduces new higher-order terms of fourth-derivative due to quantum corrections in the scalar field’s equation of motion. Then, we investigate asymptotic dynamics and general behaviour of solutions of the field equations for some interacting models of special interests in the literature. At the background level, the present interacting model exhibits the matter-dominated and de Sitter solutions which are absent in the corresponding quintessence model. Furthermore, to boost the background analysis, we study cosmological linear perturbations in the Newtonian gauge where we show how perturbations are modified by quantum corrected terms from the quadratic Generalized Uncertainty Principle. Depending on the coupling parameters, scalar perturbations show a wide range of behavior.


2019 ◽  
Vol 97 (11) ◽  
pp. 1185-1186 ◽  
Author(s):  
E.C. Gunay Demirel

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.


2017 ◽  
Vol 26 (12) ◽  
pp. 1743010 ◽  
Author(s):  
C. Sivaram

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.


2007 ◽  
Vol 16 (02n03) ◽  
pp. 463-468
Author(s):  
N. PIRES ◽  
J. S. ALCANIZ

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).


2005 ◽  
Vol 22 (4) ◽  
pp. 315-325 ◽  
Author(s):  
Luke Barnes ◽  
Matthew J. Francis ◽  
Geraint F. Lewis ◽  
Eric V. Linder

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.


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

2016 ◽  
Vol 31 (12) ◽  
pp. 1650071 ◽  
Author(s):  
Titus K. Mathew ◽  
Chinthak Murali ◽  
J. Shejeelammal

Assuming the form of the entropic dark energy (EDE) as it arises from the surface term in the Einstein–Hilbert’s action, its evolution was analyzed in an expanding flat universe. The model parameters were evaluated by constraining the model using the Union data on Type Ia supernovae. We found that in the non-interacting case, the model predicts an early decelerated phase and a later accelerated phase at the background level. The evolutions of the Hubble parameter, dark energy (DE) density, equation of state parameter and deceleration parameter were obtained. The model hardly seems to be supporting the linear perturbation growth for the structure formation. We also found that the EDE shows phantom nature for redshifts z [Formula: see text] 0.257. During the phantom epoch, the model predicts big rip effect at which both the scale factor of expansion and the DE density become infinitely large and the big rip time is found to be around 36 Giga years from now.


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