Weighing Cosmological Models with SNe Ia and Gamma Ray Burst Redshift Data

Gupta, Ranjana

doi:10.3390/universe5050102

Cited by 8 publications

(9 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As → 0, both the above expressions, Equations (39) and (40), tend to unity, i.e., the universe was strongly curved in the past. By taking Ω 0 = Ω ,0 = 0.63 from Table 1 for Equation (39), and Ω 0 = Ω ,0 = 9.0 × 10 −5 from Table 5.2 in reference [7], we get radiation density equal to matter density at ≈ 7000, which is determined by the relation: It should be mentioned that we are not trying to determine which model fits the SNe 1a data best, as this has already been done in an earlier paper [28] Our attempt is to determine the u parameter of the curvature by fitting the data.…”

Section: Resultsmentioning

confidence: 71%

The Flatness Problem and the Variable Physical Constants

Gupta

2019

Galaxies

Self Cite

View full text Add to dashboard Cite

We have used the varying physical constant approach to resolve the flatness problem in cosmology. Friedmann equations are modified to include the variability of speed of light, gravitational constant, cosmological constant, and the curvature constant. The continuity equation obtained with such modifications includes the scale factor-dependent cosmological term as well as the curvature term, along with the standard energy-momentum term. The result is that as the scale factor tends to zero (i.e., as the Big Bang is approached), the universe becomes strongly curved rather than flatter and flatter in the standard cosmology. We have used the supernovae 1a redshift versus distance modulus data to determine the curvature variation parameter of the new model, which yields a better fit to the data than the standard ΛCDM model. The universe is found to be an open type with a radius of curvature R c = 1.64 ( 1 + z ) − 3.3 c 0 / H 0 , where z is the redshift, c 0 is the current speed of light, and H 0 is the Hubble constant.

show abstract

Section: Resultsmentioning

confidence: 71%

The Flatness Problem and the Variable Physical Constants

Gupta

2019

Galaxies

Self Cite

View full text Add to dashboard Cite

show abstract

“…The Matlab curve fitting tool was used to fit the data by minimizing χ 2 and the latter was used for determining the corresponding χ 2 probability P [36]. Here χ 2 is the weighted summed square of residual of µ:…”

Section: Resultsmentioning

confidence: 99%

“…In order to assess clearly the goodness-of-fit in each category and make them comparable between categories, we decided to use the normalization method introduced in a recent paper [36]. The method is as follows:…”

Section: Resultsmentioning

confidence: 99%

Determining Evolution of Cosmological Constant, Gravitational Constant and Speed of Light Using Nonadiabatic Cosmological Model and LLR Findings

Gupta¹

2019

Galaxies

View full text Add to dashboard Cite

We have shown that the Hubble constant H0 embodies the information about the evolutionary nature of the cosmological constant Λ, gravitational constant G, and the speed of light c. We have derived expressions for the time evolution of G/c2 (≡K) and dark energy density εΛ related to Λ by explicitly incorporating the nonadiabatic nature of the universe in the Friedmann equation. We have found (dK/dt)/K = 1.8H0 and, for redshift z, εΛ,z/εΛ,0 = 0.4+0.61+z-1.52. Since the two expressions are related, we believe that the time variation of K (and therefore that of G and c) is manifested as dark energy in cosmological models. When we include the null finding of the lunar laser ranging (LLR) for (dG/dt)/G and relax the constraint that c is constant in LLR measurements, we get (dG/dt)/G = 5.4H0 and (dc/dt)/c = 1.8H0. Further, when we adapt the standard ΛCDM model for the z dependency of εΛ rather than it being a constant, we obtain surprisingly good results fitting the SNe Ia redshift z vs distance modulus µ data. An even more significant finding is that the new ΛCDM model, when parameterized with low redshift data set (z < 0.5), yields a significantly better fit to the data sets at high redshifts (z > 0.5) than the standard ΛCDM model. Thus, the new model may be considered robust and reliable enough for predicting distances of radiation emitting extragalactic redshift sources for which luminosity distance measurement may be difficult, unreliable, or no longer possible.

show abstract

“…Table 3: Numerical values from the Union 2.1 compilation + the "Hymnium" GRBs sample of χ 2 , χ 2 red and Q, where k stands for the number of parameters. The extension of the Hubble diagram to the GRBs, as an example, has been implemented in [17,11,18,19,20].…”

Section: Cardassian Cosmologymentioning

confidence: 99%

The Distance Modulus in Dark Energy and Cardassian Cosmologies via the Hypergeometric Function

Zaninetti

2019

IJAA

View full text Add to dashboard Cite

The presence of the dark energy allows both the acceleration and the expansion of the universe. In the case of a constant equation of state for dark energy we derived an analytical solution for the Hubble radius in terms of the hypergeometric function. An approximate Taylor expansion of order seven is derived for both the constant and the variable equation of state for dark energy. In the case of the Cardassian cosmology we also derived an analytical solution for the Hubble radius in terms of the hypergeometric function. The astronomical samples of the distance modulus for Supernova (SN) of type Ia allows the derivation of the involved cosmological in the case of constant equation of state, variable equation of state and Cardassian cosmology.

show abstract

Weighing Cosmological Models with SNe Ia and Gamma Ray Burst Redshift Data

Cited by 8 publications

References 36 publications

The Flatness Problem and the Variable Physical Constants

The Flatness Problem and the Variable Physical Constants

Determining Evolution of Cosmological Constant, Gravitational Constant and Speed of Light Using Nonadiabatic Cosmological Model and LLR Findings

The Distance Modulus in Dark Energy and Cardassian Cosmologies via the Hypergeometric Function

Contact Info

Product

Resources

About