Model-independent dark energy equation of state from unanchored baryon acoustic oscillations

2016 ◽  
Vol 13 ◽  
pp. 126-131 ◽  
Author(s):  
Jarah Evslin
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Equation ◽  
Acoustic Oscillations ◽  
Model Independent ◽  
Baryon Acoustic Oscillations

scholarly journals MEASURING NEUTRINO MASSES AND DARK ENERGY

2008 ◽  
Vol 23 (34) ◽  
pp. 2881-2895
Author(s):  
HUITZU TU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Neutrino Mass ◽  
Energy Equation ◽  
Mass Scale ◽  
Neutrino Masses ◽  
Acoustic Oscillations ◽  
Distance Measurements ◽  
The Galaxy ◽  
Absolute Neutrino Mass

We review some recent efforts in determining the absolute neutrino mass scale in cosmology. We illustrate in particular how distance measurements such as the baryon acoustic oscillations and the galaxy weak lensing can break the degeneracy between the neutrino mass and dark energy equation of state parameters.

scholarly journals Non-linear interacting cosmological models after Planck 2018 legacy release and the H0 tension

2020 ◽  
Vol 493 (3) ◽  
pp. 3114-3131 ◽  
Author(s):  
Supriya Pan ◽  
Weiqiang Yang ◽  
Andronikos Paliathanasis
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Observational Data ◽  
Energy Equation ◽  
Hubble Space Telescope ◽  
Hubble Constant ◽  
Acoustic Oscillations ◽  
Coincidence Problem ◽  
Linear Interaction ◽  
Non Linear

ABSTRACT Interacting dark energy models are widely renowned for giving an explanation to the cosmic coincidence problem as well as several observational issues. According to the recent observational data, and so far we are concerned with the literature, the choice of the interaction function between dark matter and dark energy is always questionable since there is no such underlying theory that could derive it. Thus, in this work we have raised this issue by proposing two new non-linear interaction functions and constrain them using cosmic microwave background (CMB) from Planck 2018, baryon acoustic oscillations (BAOs), dark energy survey and a measurement of the Hubble constant H0 from Hubble Space Telescope (HST) 2019. The dark energy equation of state is considered to be constant throughout the work and the geometry of the universe is assumed to be homogeneous and isotropic with zero spatial curvature. Our analyses report that a non-zero interaction is always allowed by the observational data and the dark energy equation of state is bent towards the phantom regime. In particular, when H0 from HST is added to Planck 2018+BAO, we find an evidence for a non-zero coupling at more than 2σ confidence level. Our analyses also report that for both the models, H0 is close to its local measurements and thus alleviating the H0 tension. In particular, one of the interacting models perfectly solves the H0 tension.

scholarly journals Dynamical dark energy after Planck CMB final release and H0 tension

2020 ◽  
Author(s):  
Weiqiang Yang ◽  
Eleonora Di Valentino ◽  
Supriya Pan ◽  
Yabo Wu ◽  
Jianbo Lu
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Hubble Space Telescope ◽  
Acoustic Oscillations ◽  
Energy Models ◽  
Bayesian Evidence ◽  
Local Measurements ◽  
Evidence Analysis ◽  
Baryon Acoustic Oscillations ◽  
Dynamical Dark Energy

Abstract In this article we compare a variety of well known dynamical dark energy models using the cosmic microwave background measurements from the 2018 Planck legacy and 2015 Planck data releases, the baryon acoustic oscillations measurements and the local measurements of H0 obtained by the SH0ES (Supernovae, H0, for the Equation of State of Dark energy) collaboration analysing the Hubble Space Telescope data. We discuss the alleviation of H0 tension, that is obtained at the price of a phantom-like dark energy equation of state. We perform a Bayesian evidence analysis to quantify the improvement of the fit, finding that all the dark energy models considered in this work are preferred against the ΛCDM scenario. Finally, among all the possibilities analyzed, the CPL model is the best one in fitting the data and solving the H0 tension at the same time. However, unfortunately, this dynamical dark energy solution is not supported by the baryon acoustic oscillations (BAO) data, and the tension is restored when BAO data are included for all the models.

scholarly journals Measuring the Hubble function with standard candle clustering

2021 ◽  
Author(s):  
Luca Amendola ◽  
Miguel Quartin
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Power Spectrum ◽  
Energy Equation ◽  
Luminosity Distance ◽  
Distortion Parameter ◽  
Peculiar Velocities ◽  
Matter Power Spectrum ◽  
Standard Candle ◽  
Model Independent

Abstract Supernova Ia magnitude surveys measure the dimensionless luminosity distance H0DL. However, from the distances alone one cannot obtain quantities like H(z) or the dark energy equation of state, unless further cosmological assumptions are imposed. Here we show that by measuring the power spectrum of density contrast and of peculiar velocities of supernovae one can estimate also H(z)/H0 regardless of background or linearly perturbed cosmology and of galaxy-matter bias. This method, dubbed Clustering of Standard Candles (CSC) also yields the redshift distortion parameter β(k, z) and the biased matter power spectrum in a model-independent way. We forecast that an optimistic (pessimistic) LSST may be able to constrain H(z)/H0 to 5–13% (9–40%) in redshift bins of Δz = 0.1 up to at least z = 0.6.

scholarly journals Observational Constraints on Dynamical Dark Energy with Pivoting Redshift

Universe ◽  
2019 ◽  
Vol 5 (11) ◽  
pp. 219 ◽  
Author(s):  
Weiqiang Yang ◽  
Supriya Pan ◽  
Eleonora Di Valentino ◽  
Emmanuel N. Saridakis
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Free Parameter ◽  
Energy Equation ◽  
Hubble Constant ◽  
Mean Value ◽  
Observational Constraints ◽  
Acoustic Oscillations ◽  
Light Curve Analysis ◽  
Full Data

We investigate the generalized Chevallier–Polarski–Linder (CPL) parametrization, which contains the pivoting redshift z p as an extra free parameter, in order to examine whether the evolution of the dark energy equation of state can be better described by a different parametrization. We use various data combinations from cosmic microwave background (CMB), baryon acoustic oscillations (BAO), redshift space distortion (RSD), weak lensing (WL), joint light curve analysis (JLA), and cosmic chronometers (CC), and we include a Gaussian prior on the Hubble constant value, in order to extract the observational constraints on various quantities. For the case of free z p we find that for all data combinations it always remains unconstrained, and there is a degeneracy with the value of the dark energy equation of state w 0 p at z p . For the case where z p is fixed to specific values, and for the full data combination, we find that with increasing z p the mean value of w 0 p slowly moves into the phantom regime, however the cosmological constant is always allowed within 1 σ confidence-level. In fact, the significant effect is that with increasing z p , the correlations between w 0 p and w a (the free parameter of the dark energy equation of state quantifying its evolution with redshift), change from negative to positive, with the case z p = 0 . 35 corresponding to no correlation. The fact that the two parameters describing the dark energy equation of state are uncorrelated for z p = 0 . 35 justifies why a non-zero pivoting redshift needs to be taken into account.

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 Nonparametric reconstruction of the dark energy equation of state from diverse data sets

2011 ◽  
Vol 84 (8) ◽  
Author(s):  
Tracy Holsclaw ◽  
Ujjaini Alam ◽  
Bruno Sansó ◽  
Herbie Lee ◽  
Katrin Heitmann ◽  
...  
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Equation ◽  
Data Sets ◽  
Diverse Data
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