scholarly journals Local determination of the Hubble constant and the deceleration parameter

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
David Camarena ◽  
Valerio Marra
Keyword(s):  
Deceleration Parameter ◽  
Hubble Constant ◽  
Local Determination

scholarly journals Redshifts and Large Scale Structures

1983 ◽  
Vol 104 ◽  
pp. 159-165
Author(s):  
G. Chincarini
Keyword(s):  
Deceleration Parameter ◽  
Large Scale ◽  
Hubble Constant ◽  
Large Scale Structures ◽  
Classical Paper ◽  
Scale Structures

The effort to measure the geometry of space by experiment, that is, the determination of the Hubble Constant, Ho, and of the deceleration parameter, qo, led toward the end of the first half of the century, to the classical paper by Humason, Mayall, and Sandage (1956). Their catalogue contains 920 redshifts collected over a twenty-year period (1935–1955). Further redshifts of galaxies were measured to refine such determinations and to study the dynamics of clusters (Zwicky 1933).

scholarly journals 47. Cosmology

1976 ◽  
Vol 16 (3) ◽  
pp. 137-157
Author(s):  
M. S. Longair
Keyword(s):  
Deceleration Parameter ◽  
Hubble Constant ◽  
Density Parameter ◽  
Massive Galaxies ◽  
A Value ◽  
The Mean ◽  
Points Of View ◽  
The Universe

A major procedural advance in the determination of the H0 and Ω has been that the problem is now being attacked from many different points of view and to some extent the observations are converging on preferred values of H0 and Ω (Ω = density parameter = 8πGρ0/3H0 where ρ0 is the mean density of matter in the Universe and H0 is the Hubble constant; Ω = 2q0 where q0 is the deceleration parameter). The classical approaches through the redshift-magnitude relation for the most massive galaxies in clusters suggest a value of H0 = 60 km s-1 Mpc (see the review by Tammann in IAU Symp. 63).

scholarly journals Cosmological constrains on minimally and non-minimally coupled scalar field models

2019 ◽  
Author(s):  
Zahra Davari ◽  
Valerio Marra ◽  
Mohammad Malekjani
Keyword(s):  
Scalar Field ◽  
Hubble Constant ◽  
Information Criteria ◽  
Accelerated Expansion ◽  
Scalar Field Models ◽  
Expansion Of The Universe ◽  
Cosmological Data ◽  
Local Determination ◽  
The One

Abstract We study the minimally and non-minimally coupled scalar field models as possible alternatives for dark energy, the mysterious energy component that is driving the accelerated expansion of the universe. After discussing the dynamics at both the background and perturbation level, we confront the two models with the latest cosmological data. After obtaining updated constraints on their parameters we perform model selection using the basic information criteria. We found that the ΛCDM model is strongly favored when the local determination of the Hubble constant is not considered and that this statement is weakened once local H0 is included in the analysis. We calculate the parameter combination $S_8=\sigma _8\sqrt{\Omega _{m}/0.3}$ and show the decrement of the tension with respect to the Planck results in the case of minimally and non-minimally coupled scalar field models. Finally, for the coupling constant between DE and gravity, we obtain the constraint $\xi \simeq -0.06^{+0.19}_{-0.19}$, approaching the one from solar system tests |ξ| ≲ 10−2 and comparable to the conformal value ξ = 1/6 at 1σ uncertainty.

On the lyman problem

Open Physics ◽  
2003 ◽  
Vol 1 (2) ◽  
Author(s):  
Václav Kolár
Keyword(s):  
Classical Field Theory ◽  
Integral Boundary ◽  
Effective Measure ◽  
Local Determination ◽  
Vorticity Flux ◽  
Effective Part ◽  
Definition Of ◽  
Vorticity Transport ◽  
Creation Rate

AbstractThis paper attempts to answer Lyman's question (1990) on the non-uniqueness in defining the 3D measure of the boundary vorticity-creation rate. Firstly, a straightforward analysis of the vorticity equation introduces a definition of a general vorticity flux-density tensor and its ‘effective’ part. The approach is strictly based on classical field theory and is independent of the constitutive structure of continuous medium. Secondly, the fundamental question posed by Lyman dealing with the ambiguity of the 3D measure of the boundary vorticity-creation rate for incompressible flow is discussed. It is shown that the original 3D measure (for an incompressible Newtonian fluid defined by Panton 1984), which is reminiscent of an analogy to Fourier's law, is in its character ‘effective’ and plays a crucial role in the prognostic vorticity transport equation. The alternative 3D measure proposed by Lyman includes, on the other hand, a ‘non-effective’ part, which plays a role in the local determination of the ‘effective’ measure as well as in a certain diagnostic integral boundary condition.

scholarly journals The Hubble constant from eight time-delay galaxy lenses

2020 ◽  
Vol 501 (1) ◽  
pp. 784-801 ◽  
Author(s):  
Philipp Denzel ◽  
Jonathan P Coles ◽  
Prasenjit Saha ◽  
Liliya L R Williams
Keyword(s):  
Time Delay ◽  
Hubble Constant ◽  
Free Form ◽  
Microwave Background ◽  
Form Analysis ◽  
Systematic Uncertainties ◽  
Type Ia ◽  
Modelling Strategies ◽  
Supernovae Type Ia

ABSTRACT We present a determination of the Hubble constant from the joint, free-form analysis of eight strongly, quadruply lensing systems. In the concordance cosmology, we find $H_0{} = 71.8^{+3.9}_{-3.3}\, \mathrm{km}\, \mathrm{s}^{-1}\, \mathrm{Mpc}^{-1}{}{}$ with a precision of $4.97{{\ \rm per\ cent}}$. This is in agreement with the latest measurements from supernovae Type Ia and Planck observations of the cosmic microwave background. Our precision is lower compared to these and other recent time-delay cosmography determinations, because our modelling strategies reflect the systematic uncertainties of lensing degeneracies. We furthermore are able to find reasonable lensed image reconstructions by constraining to either value of H0 from local and early Universe measurements. This leads us to conclude that current lensing constraints on H0 are not strong enough to break the ‘Hubble tension’ problem of cosmology.

scholarly journals SNe Ia Redshift in a Nonadiabatic Universe

Universe ◽  
2018 ◽  
Vol 4 (10) ◽  
pp. 104 ◽  
Author(s):  
Rajendra Gupta
Keyword(s):  
Cosmological Constant ◽  
Deceleration Parameter ◽  
Hubble Constant ◽  
Cosmological Models ◽  
Single Parameter ◽  
New Approach ◽  
Cosmological Principle ◽  
Flat Universe ◽  
Λcdm Model ◽  
Two Parameters

By relaxing the constraint of adiabatic universe used in most cosmological models, we have shown that the new approach provides a better fit to the supernovae Ia redshift data with a single parameter, the Hubble constant H0, than the standard ΛCDM model with two parameters, H0 and the cosmological constant Λ related density, ΩΛ. The new approach is compliant with the cosmological principle. It yields the H0 = 68.28 (±0.53) km s−1 Mpc−1 with an analytical value of the deceleration parameter q0 = −0.4. The analysis presented is for a matter-only, flat universe. The cosmological constant Λ may thus be considered as a manifestation of a nonadiabatic universe that is treated as an adiabatic universe.

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