scholarly journals Comparative analysis of model-independent methods for exploring the nature of dark energy

2013 ◽  
Vol 88 (6) ◽  
Author(s):  
Savvas Nesseris ◽  
Juan García-Bellido
Keyword(s):  
Dark Energy ◽  
Comparative Analysis ◽  
Model Independent

scholarly journals Model-independent calibrations of gamma-ray bursts using machine learning

2021 ◽  
Vol 503 (3) ◽  
pp. 4581-4600
Author(s):  
Orlando Luongo ◽  
Marco Muccino
Keyword(s):  
Machine Learning ◽  
Dark Energy ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Bayesian Regression ◽  
Machine Learning Techniques ◽  
Acoustic Oscillations ◽  
Chi Square ◽  
Model Independent ◽  
Chi Square Analysis

ABSTRACT We alleviate the circularity problem, whereby gamma-ray bursts are not perfect distance indicators, by means of a new model-independent technique based on Bézier polynomials. We use the well consolidate Amati and Combo correlations. We consider improved calibrated catalogues of mock data from differential Hubble rate points. To get our mock data, we use those machine learning scenarios that well adapt to gamma-ray bursts, discussing in detail how we handle small amounts of data from our machine learning techniques. We explore only three machine learning treatments, i.e. linear regression, neural network, and random forest, emphasizing quantitative statistical motivations behind these choices. Our calibration strategy consists in taking Hubble’s data, creating the mock compilation using machine learning and calibrating the aforementioned correlations through Bézier polynomials with a standard chi-square analysis first and then by means of a hierarchical Bayesian regression procedure. The corresponding catalogues, built up from the two correlations, have been used to constrain dark energy scenarios. We thus employ Markov chain Monte Carlo numerical analyses based on the most recent Pantheon supernova data, baryonic acoustic oscillations, and our gamma-ray burst data. We test the standard ΛCDM model and the Chevallier–Polarski–Linder parametrization. We discuss the recent H0 tension in view of our results. Moreover, we highlight a further severe tension over Ωm and we conclude that a slight evolving dark energy model is possible.

scholarly journals Model-independent constraints on dark energy evolution from low-redshift observations

2019 ◽  
Vol 484 (4) ◽  
pp. 4484-4494 ◽  
Author(s):  
Salvatore Capozziello ◽  
Ruchika ◽  
Anjan A Sen
Keyword(s):  
Dark Energy ◽  
Energy Evolution ◽  
Model Independent

scholarly journals Covariant extrinsic gravity and the geometric origin of dark energy

2015 ◽  
Vol 24 (03) ◽  
pp. 1550027 ◽  
Author(s):  
S. Jalalzadeh ◽  
T. Rostami
Keyword(s):  
Dark Energy ◽  
Density Parameter ◽  
Field Equations ◽  
Yang Mills ◽  
Geometric Origin ◽  
Model Independent ◽  
Bulk Space ◽  
Mills Field ◽  
Matter Fields ◽  
Good Agreement

In this paper, we construct the covariant or model independent induced Einstein–Yang–Mills field equations on a four-dimensional brane embedded isometrically in an D-dimensional bulk space, assuming the matter fields are confined to the brane. Applying this formalism to cosmology, we derive the generalized Friedmann equations. We derive the density parameter of dark energy in terms of width of the brane, normal curvature radii and the number of extra large dimensions. We show that dark energy could actually be the manifestation of the local extrinsic shape of the brane. It is shown that the predictions of this model are in good agreement with observation if we consider an 11-dimensional bulk space.

scholarly journals Measurements of $$H_0$$ and reconstruction of the dark energy properties from a model-independent joint analysis

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Alexander Bonilla ◽  
Suresh Kumar ◽  
Rafael C. Nunes
Keyword(s):  
Dark Energy ◽  
Sound Speed ◽  
Hubble Constant ◽  
State Parameter ◽  
Independent Method ◽  
Joint Analysis ◽  
Acoustic Oscillations ◽  
Type Ia ◽  
Model Independent ◽  
Supernova Type Ia

AbstractGaussian processes (GP) provide an elegant and model-independent method for extracting cosmological information from the observational data. In this work, we employ GP to perform a joint analysis by using the geometrical cosmological probes such as Supernova Type Ia (SN), Cosmic chronometers (CC), Baryon Acoustic Oscillations (BAO), and the H0LiCOW lenses sample to constrain the Hubble constant $$H_0$$ H 0 , and reconstruct some properties of dark energy (DE), viz., the equation of state parameter w, the sound speed of DE perturbations $$c^2_s$$ c s 2 , and the ratio of DE density evolution $$X = \rho _\mathrm{de}/\rho _\mathrm{de,0}$$ X = ρ de / ρ de , 0 . From the joint analysis SN+CC+BAO+H0LiCOW, we find that $$H_0$$ H 0 is constrained at 1.1% precision with $$H_0 = 73.78 \pm 0.84\ \hbox {km}\ \hbox {s}^{-1}\,\hbox {Mpc}^{-1}$$ H 0 = 73.78 ± 0.84 km s - 1 Mpc - 1 , which is in agreement with SH0ES and H0LiCOW estimates, but in $$\sim 6.2 \sigma $$ ∼ 6.2 σ tension with the current CMB measurements of $$H_0$$ H 0 . With regard to the DE parameters, we find $$c^2_s < 0$$ c s 2 < 0 at $$\sim 2 \sigma $$ ∼ 2 σ at high z, and the possibility of X to become negative for $$z > 1.5$$ z > 1.5 . We compare our results with the ones obtained in the literature, and discuss the consequences of our main results on the DE theoretical framework.

scholarly journals Model-independent constraints on dark energy and modified gravity with the SKA

2015 ◽  
Author(s):  
Gongbo Zhao ◽  
D. J. Bacon ◽  
Roy Maartens ◽  
Mario Santos ◽  
Alvise Raccanelli
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Model Independent
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