scholarly journals Resolving the Hubble Constant Discrepancy: Revisiting the Effect of Local Environments

2020 ◽  
Vol 2 (1) ◽  
pp. 94-96
Author(s):  
Dennis M Doren ◽  
James Harasymiw
Keyword(s):  
Mass Density ◽  
Hubble Constant ◽  
Local Environment ◽  
Expansion Rate ◽  
Local Environments ◽  
The Universe

Studies have found two differing sets of figures for the Hubble constant without clear direction for resolution of that difference. This article offers a direction for reconciling the measurement discrepancy. Research is reviewed and theory is described that indicate the resolution may be found in revisiting how the degree of mass in local environments affects computations. The idea that the expansion rate of the universe is invariably uniform is discounted, to be replaced by a range of figures depending on the mass density of the local environment underlying the measurement.

scholarly journals Local Large-Scale Structure and the Assumption of Homogeneity

2014 ◽  
Vol 11 (S308) ◽  
pp. 295-298 ◽  
Author(s):  
Ryan C. Keenan ◽  
Amy J. Barger ◽  
Lennox L. Cowie
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Near Infrared ◽  
Mass Density ◽  
Hubble Constant ◽  
A Value ◽  
Accelerating Expansion ◽  
Luminous Matter ◽  
Local Measurements ◽  
The Universe

AbstractOur recent estimates of galaxy counts and the luminosity density in the near-infrared (Keenan et al. 2010, 2012) indicated that the local universe may be under-dense on radial scales of several hundred megaparsecs. Such a large-scale local under-density could introduce significant biases in the measurement and interpretation of cosmological observables, such as the inferred effects of dark energy on the rate of expansion. In Keenan et al. (2013), we measured the K-band luminosity density as a function of distance from us to test for such a local under-density. We made this measurement over the redshift range 0.01 < z < 0.2 (radial distances D ~ 50 - 800 h70−1 Mpc). We found that the shape of the K-band luminosity function is relatively constant as a function of distance and environment. We derive a local (z < 0.07, D < 300 h70−1 Mpc) K-band luminosity density that agrees well with previously published studies. At z > 0.07, we measure an increasing luminosity density that by z ~ 0.1 rises to a value of ~ 1.5 times higher than that measured locally. This implies that the stellar mass density follows a similar trend. Assuming that the underlying dark matter distribution is traced by this luminous matter, this suggests that the local mass density may be lower than the global mass density of the universe at an amplitude and on a scale that is sufficient to introduce significant biases into the measurement of basic cosmological observables. At least one study has shown that an under-density of roughly this amplitude and scale could resolve the apparent tension between direct local measurements of the Hubble constant and those inferred by Planck team. Other theoretical studies have concluded that such an under-density could account for what looks like an accelerating expansion, even when no dark energy is present.

Ω0 Concordance

2005 ◽  
Vol 201 ◽  
pp. 271-281
Author(s):  
Masataka. Fukugita
Keyword(s):  
Dark Matter ◽  
Cosmological Constant ◽  
Structure Formation ◽  
Cold Dark Matter ◽  
Mass Density ◽  
Hubble Constant ◽  
Density Parameter ◽  
Microwave Background ◽  
The Hierarchical Structure ◽  
The Universe

The determinations of the mass density parameter Ω0 are examined with a particular emphasis given to the new cosmic microwave background (CMB) experiments. It is shown that the Ω0 and the Hubble constant H0 from CMB are quite consistent with those from other observations with the aid of the hierarchical structure formation models based on cold dark matter dominance with the cosmological constant that makes the universe flat. The concordance value of Ω0 is 0.25-0.45.

Is Our Universe Accelerating Dynamics Fractional Order?

2015 ◽  
Author(s):  
Caibin Zeng ◽  
YangQuan Chen ◽  
Igor Podlubny
Keyword(s):  
Fundamental Solution ◽  
Fractional Order ◽  
Exponential Function ◽  
Dynamical Equation ◽  
Hubble Constant ◽  
Expansion Rate ◽  
Fractional Dynamics ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

In this paper, a fractional dynamics approach is used to characterize the observed accelerating expansion of the universe. We claim that the evolution of accelerating expansion obeys an α-exponential function, which is the fundamental solution of linear fractional order dynamical equation. We find that the Hubble constant is 67.8807, 68.2546, and 67.9119 for all redshift z < 1.5, z < 1, and z < 0.1 based on the dataset collected by the Supernova Cosmology Project. Furthermore, we verify that the expansion rate of our universe is speeding up and actually obeys a Mittag-Leffler law.

scholarly journals The background Friedmannian Hubble constant in relativistic inhomogeneous cosmology and the age of the Universe

2017 ◽  
Vol 598 ◽  
pp. A111 ◽  
Author(s):  
Boudewijn F. Roukema ◽  
Pierre Mourier ◽  
Thomas Buchert ◽  
Jan J. Ostrowski
Keyword(s):  
Energy Parameter ◽  
Hubble Constant ◽  
Expansion Rate ◽  
De Sitter ◽  
Low Mass Stars ◽  
Inhomogeneous Cosmology ◽  
Cosmological Time ◽  
Low Mass ◽  
Age Of The Universe ◽  
The Universe

Context. In relativistic inhomogeneous cosmology, structure formation couples to average cosmological expansion. A conservative approach to modelling this assumes an Einstein-de Sitter model (EdS) at early times and extrapolates this forward in cosmological time as a “background model” against which average properties of today’s Universe can be measured. Aims. This modelling requires adopting an early-epoch-normalised background Hubble constant Hbg1. Methods. Here, we show that the ΛCDM model can be used as an observational proxy to estimate Hbg1 rather than choose it arbitrarily. We assume (i) an EdS model at early times; (ii) a zero dark energy parameter; (iii) bi-domain scalar averaging-division of the spatial sections into over- and underdense regions; and (iv) virialisation (stable clustering) of collapsed regions. Results. We find Hbg1= 37.7 ± 0.4 km s-1/ Mpc (random error only) based on a Planck ΛCDM observational proxy. Conclusions. Moreover, since the scalar-averaged expansion rate is expected to exceed the (extrapolated) background expansion rate, the expected age of the Universe should be much younger than 2/(3Hbg1) = 17.3 Gyr. The maximum stellar age of Galactic bulge microlensed low-mass stars (most likely: 14.7 Gyr; 68% confidence: 14.0–15.0 Gyr) suggests an age of about a Gyr older than the (no-backreaction) ΛCDM estimate.

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 Natural inflation after Planck 2018

2022 ◽  
Vol 2022 (01) ◽  
pp. 022
Author(s):  
Nina K. Stein ◽  
William H. Kinney
Keyword(s):  
Symmetry Breaking ◽  
High Precision ◽  
Confidence Region ◽  
Hubble Constant ◽  
Current Data ◽  
Electroweak Symmetry Breaking ◽  
Observational Constraints ◽  
Electroweak Symmetry ◽  
History Of ◽  
The Universe

Abstract We calculate high-precision constraints on Natural Inflation relative to current observational constraints from Planck 2018 + BICEP/Keck(BK15) Polarization + BAO on r and n S, including post-inflationary history of the universe. We find that, for conventional post-inflationary dynamics, Natural Inflation with a cosine potential is disfavored at greater than 95% confidence out by current data. If we assume protracted reheating characterized by w̅>1/3, Natural Inflation can be brought into agreement with current observational constraints. However, bringing unmodified Natural Inflation into the 68% confidence region requires values of T re below the scale of electroweak symmetry breaking. The addition of a SHOES prior on the Hubble Constant H 0 only worsens the fit.

scholarly journals Distance Indicators in the Magellanic Clouds

1983 ◽  
Vol 6 ◽  
pp. 209-216 ◽  
Author(s):  
J.A. Graham
Keyword(s):  
Chemical Evolution ◽  
Comparative Studies ◽  
Hubble Constant ◽  
Magellanic Clouds ◽  
Distance Scale ◽  
Stellar Systems ◽  
Age Range ◽  
Distance Indicators ◽  
The Universe

In talking about the overall distance scale of the Universe and the Hubble Constant, the Magellanic Clouds are good places to start. They are stellar systems large enough to contain stars, clusters and nebulae of all types, covering a wide age range. With modern telescopes and detectors, we are able to observe stars from the very bright down to those fainter intrinsically than our own Sun. From comparative studies, we may thus establish our basic calibrations of bright objects before moving out to measure the Universe at large. At the same time, the fact that both Magellanic Clouds are independently evolving galaxies, enables us to separate the effects of stellar age and chemical evolution on the calibrations that we make.

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