scholarly journals Cosmological models, observational data and tension in Hubble constant

2020 ◽  
pp. 1-20
Author(s):  
G.S. Sharov ◽  
E.S. Sinyakov
Keyword(s):  
Observational Data ◽  
Hubble Parameter ◽  
Background Radiation ◽  
Hubble Constant ◽  
Cosmological Models ◽  
Model Parameters ◽  
Data Sets ◽  
Type Ia ◽  
Data Points ◽  
Ia Supernovae

We analyze how predictions of cosmological models depend on a choice of described observational data, restrictions on flatness, and how this choice can alleviate the H tension. These effects are demonstrated in the wCDM model in comparison with the standard ΛCDM model. We describe the Pantheon sample observations of Type Ia supernovae, 31 Hubble parameter data points H(z) from cosmic chronometers, the extended sample with 57 H(z) data points and observational manifestations of cosmic microwave background radiation (CMB). For the wCDM and ΛCDM models in the flat case and with spatial curvature, we calculate χfunctions for all observed data in different combinations, estimate optimal values of model parameters and their expected intervals. For both considered models the results essentially depend on a choice of data sets. In particular, for the wCDM model with H(z) data, supernovae and CMB the 1σ estimations may vary from H = 67.52km /(s·Mpc) (for all N = 57 Hubble parameter data points) up to H = 70.87 /(s·Mpc) for the flat case (k = 0) and N = 31. These results might be a hint how to alleviate the problem of H tension: different estimates of the Hubble constant may be connected with filters and a choice of observational data.

scholarly journals How does an incomplete sky coverage affect the Hubble Constant variance?

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Carlos A. P. Bengaly ◽  
Uendert Andrade ◽  
Jailson S. Alcaniz
Keyword(s):  
Hubble Constant ◽  
Real Data ◽  
Data Sets ◽  
Constant Variance ◽  
Uniform Distributions ◽  
Constant Tension ◽  
Type Ia ◽  
Data Points ◽  
Standard Cosmological Model ◽  
Celestial Sphere

Abstract We address the $$\simeq 4.4\sigma $$≃4.4σ tension between local and the CMB measurements of the Hubble Constant using simulated Type Ia Supernova (SN) data-sets. We probe its directional dependence by means of a hemispherical comparison through the entire celestial sphere as an estimator of the $$H_0$$H0 cosmic variance. We perform Monte Carlo simulations assuming isotropic and non-uniform distributions of data points, the latter coinciding with the real data. This allows us to incorporate observational features, such as the sample incompleteness, in our estimation. We obtain that this tension can be alleviated to $$3.4\sigma $$3.4σ for isotropic realizations, and $$2.7\sigma $$2.7σ for non-uniform ones. We also find that the $$H_0$$H0 variance is largely reduced if the data-sets are augmented to 4 and 10 times the current size. Future surveys will be able to tell whether the Hubble Constant tension happens due to unaccounted cosmic variance, or whether it is an actual indication of physics beyond the standard cosmological model.

scholarly journals A measurement of the Hubble constant from Type II supernovae

2020 ◽  
Vol 496 (3) ◽  
pp. 3402-3411 ◽  
Author(s):  
T de Jaeger ◽  
B E Stahl ◽  
W Zheng ◽  
A V Filippenko ◽  
A G Riess ◽  
...  
Keyword(s):  
Cold Dark Matter ◽  
Background Radiation ◽  
Hubble Constant ◽  
Systematic Errors ◽  
Host Galaxy ◽  
Microwave Background Radiation ◽  
Type Ia ◽  
Cepheid Variables ◽  
Red Giant ◽  
Ia Supernovae

ABSTRACT Progressive increases in the precision of the Hubble-constant measurement via Cepheid-calibrated Type Ia supernovae (SNe Ia) have shown a discrepancy of ∼4.4σ with the current value inferred from Planck satellite measurements of the cosmic microwave background radiation and the standard $\Lambda $cold dark matter (ΛCDM) cosmological model. This disagreement does not appear to be due to known systematic errors and may therefore be hinting at new fundamental physics. Although all of the current techniques have their own merits, further improvement in constraining the Hubble constant requires the development of as many independent methods as possible. In this work, we use SNe II as standardisable candles to obtain an independent measurement of the Hubble constant. Using seven SNe II with host-galaxy distances measured from Cepheid variables or the tip of the red giant branch, we derive H$_0= 75.8^{+5.2}_{-4.9}$ km s−1 Mpc−1 (statistical errors only). Our value favours that obtained from the conventional distance ladder (Cepheids + SNe Ia) and exhibits a difference of 8.4 km s−1 Mpc−1 from the Planck + ΛCDM value. Adding an estimate of the systematic errors (2.8 km s−1 Mpc−1) changes the ∼1.7σ discrepancy with Planck +ΛCDM to ∼1.4σ. Including the systematic errors and performing a bootstrap simulation, we confirm that the local H0 value exceeds the value from the early Universe with a confidence level of 95 per cent. As in this work, we only exchange SNe II for SNe Ia to measure extragalactic distances, we demonstrate that there is no evidence that SNe Ia are the source of the H0 tension.

scholarly journals Probing cosmic opacity with the type Ia supernovae and Hubble parameter

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Bing Xu ◽  
Kaituo Zhang ◽  
Qihong Huang
Keyword(s):  
Hubble Parameter ◽  
Likelihood Function ◽  
Nuisance Parameter ◽  
Hubble Constant ◽  
Absolute Magnitude ◽  
Type Ia Supernovae ◽  
Spatial Curvature ◽  
Type Ia ◽  
Ia Supernovae ◽  
Best Fit

AbstractIn this paper, we probe the cosmic opacity with the newest Pantheon type Ia supernovae (SNIa) and the observational Hubble parameter $$\left( H(z)\right) $$ H ( z ) data based on the $$\Lambda $$ Λ CDM and wCDM models with or without spatial curvature. In the analysis, we marginalize the likelihood function of SNIa data over the pertinent nuisance parameter $${\mathcal {M}}$$ M , a combination of the absolute magnitude of SNIa $$M_{\mathrm{B}}$$ M B and the Hubble constant $$H_0$$ H 0 , with a flat prior. Two parameterizations of the optical depth $$\tau (z)$$ τ ( z ) associated to the cosmic absorption, namely $$\tau (z)=2\varepsilon z$$ τ ( z ) = 2 ε z and $$\tau (z)= (1+z)^{2\varepsilon }-1$$ τ ( z ) = ( 1 + z ) 2 ε - 1 , are adopted. We find that the results are not sensitive to the fiducial cosmological models, the spatial curvature and parameterizations of $$\tau (z)$$ τ ( z ) . Moreover, the results from the Pantheon data alone are consistent with a transparent universe ($$\varepsilon =0$$ ε = 0 ). And once the H(z) data is combined, $$\varepsilon =0$$ ε = 0 falls within the 68% confidence level (CL) of the best fit when a flat $$H_0$$ H 0 prior or the distance priors are used, while it falls within the 95% CL when a Gaussian distribution prior of $$H_0=74.03\pm 1.42$$ H 0 = 74.03 ± 1.42 km $$\mathrm {s}^{-1}\, \mathrm {Mpc}^{-1}$$ s - 1 Mpc - 1 is used.

scholarly journals SNe data analysis in variable speed of light cosmologies without cosmological constant

2014 ◽  
Vol 29 (24) ◽  
pp. 1450103 ◽  
Author(s):  
Pengfei Zhang ◽  
Xinhe Meng
Keyword(s):  
Dark Energy ◽  
Scale Factor ◽  
Model Parameters ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Data Sets ◽  
Variable Speed ◽  
Speed Of Light ◽  
Type Ia ◽  
Ia Supernovae

In this work, we aim to show the possibilities of the variable speed of light (VSL) theory in explaining the type Ia supernovae (SNe) observations without introducing dark energy. The speed of light is assumed to be scale factor-dependent, which is the most popular assumption in VSL theory. We show the modified calculation of the distance modulus and the validity of the redshift-scale factor relation in VSL theory. Three different models of VSL are tested SNe data-sets with proper constraints on the model parameters. The comparison of the three models and flat ΛCDM in distance modulus is showed. Some basic problems and the difficulties of the confirmation of the VSL theory are also discussed.

scholarly journals The effects of peculiar velocities in SN Ia environments on the local H0 measurement

2020 ◽  
Vol 500 (3) ◽  
pp. 3728-3742
Author(s):  
Thomas M Sedgwick ◽  
Chris A Collins ◽  
Ivan K Baldry ◽  
Philip A James
Keyword(s):  
Hubble Constant ◽  
Density Parameter ◽  
Host Galaxies ◽  
Peculiar Velocities ◽  
Standard Candle ◽  
Modern Cosmology ◽  
Type Ia ◽  
The Difference ◽  
Ia Supernovae ◽  
Distance Indicators

ABSTRACT The discrepancy between estimates of the Hubble constant (H0) measured from local (z ≲  0.1) scales and from scales of the sound horizon is a crucial problem in modern cosmology. Peculiar velocities (vpec) of standard candle distance indicators can systematically affect local H0 measurements. We here use 2MRS galaxies to measure the local galaxy density field, finding a notable z  <  0.05 underdensity in the SGC-6dFGS region of 27  ±  2 per cent. However, no strong evidence for a ‘Local Void’ pertaining to the full 2MRS sky coverage is found. Galaxy densities are used to measure a density parameter, Δϕ+−, which we introduce as a proxy for vpec that quantifies density gradients along a supernova (SN) line of sight. Δϕ+− is found to correlate with local H0 estimates from 88 Pantheon Type Ia supernovae (SNe Ia; 0.02  <  z  <  0.05). Density structures on scales of ∼50 Mpc are found to correlate strongest with H0 estimates in both the observational data and in mock data from the MDPL2-Galacticus simulation. Using trends of H0 with Δϕ+−, we can correct for the effects of density structure on local H0 estimates, even in the presence of biased vpec. However, the difference in the inferred H0 estimate with and without the peculiar velocity correction is limited to < 0.1  per cent. We conclude that accounting for environmentally induced peculiar velocities of SN Ia host galaxies does not resolve the tension between local and CMB-derived H0 estimates.

scholarly journals COSMOLOGICAL CONSTRAINTS FOR THE COSMIC DEFECT THEORY

2011 ◽  
Vol 20 (06) ◽  
pp. 1039-1051 ◽  
Author(s):  
NINFA RADICELLA ◽  
MAURO SERENO ◽  
ANGELO TARTAGLIA
Keyword(s):  
Large Scale ◽  
Hubble Constant ◽  
Big Bang ◽  
Nuclear Species ◽  
Type Ia ◽  
Species Abundances ◽  
Age Of The Universe ◽  
Ia Supernovae ◽  
The Big Bang ◽  
The Universe

The cosmic defect theory has been confronted with four observational constraints: primordial nuclear species abundances emerging from the big bang nucleosynthesis; large scale structure formation in the Universe; cosmic microwave background acoustic scale; luminosity distances of type Ia supernovae. The test has been based on a statistical analysis of the a posteriori probabilities for three parameters of the theory. The result has been quite satisfactory and such that the performance of the theory is not distinguishable from that of the ΛCDM theory. The use of the optimal values of the parameters for the calculation of the Hubble constant and the age of the Universe confirms the compatibility of the cosmic defect approach with observations.

scholarly journals Progenitors of type Ia supernovae

2016 ◽  
Vol 25 (10) ◽  
pp. 1630024 ◽  
Author(s):  
Keiichi Maeda ◽  
Yukikatsu Terada
Keyword(s):  
Observational Data ◽  
Current Situation ◽  
Type Ia Supernovae ◽  
Single Population ◽  
Type Ia ◽  
Ia Supernovae

Natures of progenitors of type Ia Supernovae (SNe Ia) have not yet been clarified. There has been long and intensive discussion on whether the so-called single degenerate (SD) scenario or the double degenerate (DD) scenario, or anything else, could explain a major population of SNe Ia, but the conclusion has not yet been reached. With rapidly increasing observational data and new theoretical ideas, the field of studying the SN Ia progenitors has been quickly developing, and various new insights have been obtained in recent years. This paper aims at providing a summary of the current situation regarding the SN Ia progenitors, both in theory and observations. It seems difficult to explain the emerging diversity seen in observations of SNe Ia by a single population, and we emphasize that it is important to clarify links between different progenitor scenarios and different sub-classes of SNe Ia.

A probe of cosmological models in modified teleparallel gravity

2021 ◽  
pp. 2150208
Author(s):  
Archana Dixit ◽  
Anirudh Pradhan ◽  
Dinesh Chandra Maurya
Keyword(s):  
Hubble Constant ◽  
Teleparallel Gravity ◽  
Cosmological Term ◽  
Cosmological Models ◽  
Model Parameters ◽  
Late Time ◽  
General Function ◽  
Eos Parameter ◽  
Variable Cosmological Term ◽  
Present Universe

In this paper, we have investigated the physical behavior of cosmological models in modified Teleparallel gravity with a general function [Formula: see text] where [Formula: see text] and [Formula: see text] are model parameters and [Formula: see text] is the torsion scalar. We have considered a homogeneous and isotropic Friedman universe filled with perfect fluid. We have derived the deceleration parameter [Formula: see text] in terms of equation of state (EoS) parameter [Formula: see text] and Hubble parameter [Formula: see text]. We have investigated the variation of [Formula: see text] over the observed values of Hubble constant in various observations within the range of redshift [Formula: see text]. Also, we have studied effective energy density [Formula: see text], effective pressure [Formula: see text] and effective EoS parameter [Formula: see text]. We have observed that the second term of [Formula: see text] function behaves just like variable cosmological term [Formula: see text] ([Formula: see text]) at late-time universe and causes the acceleration in expansion and works just like dark energy candidates. Also, we have evaluated the age of the present universe for various stages of matter [Formula: see text] and various [Formula: see text] functions.

scholarly journals First cosmological results using Type Ia supernovae from the Dark Energy Survey: measurement of the Hubble constant

2019 ◽  
Vol 486 (2) ◽  
pp. 2184-2196 ◽  
Author(s):  
E Macaulay ◽  
R C Nichol ◽  
D Bacon ◽  
D Brout ◽  
T M Davis ◽  
...  
Keyword(s):  
Dark Energy ◽  
Hubble Constant ◽  
Type Ia Supernovae ◽  
Distance Measurements ◽  
Dark Energy Survey ◽  
Systematic Uncertainties ◽  
Type Ia ◽  
Ia Supernovae ◽  
Energy Survey ◽  
Inverse Distance

ABSTRACT We present an improved measurement of the Hubble constant (H0) using the ‘inverse distance ladder’ method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) at redshift 0.018 < z < 0.85 to existing distance measurements of 122 low-redshift (z < 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations (BAOs). Whereas traditional measurements of H0 with SNe Ia use a distance ladder of parallax and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H0 = 67.8 ± 1.3 km s−1 Mpc−1 (statistical and systematic uncertainties, 68 per cent confidence). Our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H0 value is consistent with estimates derived from the Cosmic Microwave Background assuming a ΛCDM universe.

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