Consequences on variable Λ-models from distant type Ia supernovae and compact radio sources

By R. G. Vishwakarma. 2000

151 citations recorded by the source corpus.

We study the magnitude-redshift relation for the type?Ia supernovae data and the angular size-redshift relation for the updated compact radio sources data (from Gurvits et?al) by considering four variable ?-models: ?~S-2, ?~H2, ?~? and ?~t-2. It is found that all the variable ?-models, as well as the constant ?-Friedmann model, fit the supernovae data equally well with ?2/dof?1 and require non-zero, positive values of ? and an accelerating expansion of the universe. The estimates of the density parameter for the variable ?-models are found to be higher than those for the constant ?-Friedmann model. From the compact radio sources data, it is found, by assuming the no-evolution hypothesis, that the Gurvits et al model (Friedmann model with ? = 0) is not the best-fitting model for the constant ? case. The best-fitting Friedmann model (with constant ?) is found to be a low-density, vacuum-dominated accelerating universe. The fits of this data set to the (variable, as well as, constant ?-) models are found to be very good with ?2/dof?0.5 and require non-zero, positive values of ? with either sign of the deceleration parameter. However, for realistic values of the matter density parameter, the only interesting solutions are (a) estimated from the supernovae data: the best-fitting solutions for the flat models (including the constant ? case); (b) estimated from the radio sources data: the global best-fitting solutions for the models ?~H2 and ?~?, the best-fitting solution for the flat model with ? = {}constant and the Gurvits et al model. It is noted that, as in the case of recent cosmic microwave background analyses, the data sets seem to favour a spherical universe (k>0).

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/6ccd9c930963ea769e9ffe9e3791b7a379e7d3d9

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Citations in the corpus

A Model-Independent Determination of the Expansion and Acceleration Rates of the Universe as a Function of Redshift and Constraints on Dark Energy (2003, methodology): “In addition to the use of FR IIb radio galaxies addressed here, other methods of using radio galaxies and quasars to determine coordinate distances are discussed by Buchalter et al. (1998), Gurvits, Kellermann, & Frey (1999), Vishwakarma (2001), Lima & Alcaniz (2002), and Chen & Ratra (2003).”
First Evidence of Running Cosmic Vacuum: Challenging the Concordance Model (2016, background): “Many other works are available in the literature, the reader can consult the reviews e.g. by Overduin & Cooperstock (1998), Vishwakarma (2001), 2 Solà (2013), and references therein.”
The Cosmological Constant and Dark Energy (2002, unknown): “Constraints on the cosmological parameters from the Gurvits et al. data are discussed by Vishwakarma (2001), Lima and Alcaniz (2002), Chen and Ratra (2003), and references therein, and constraints based on the radio galaxy data are discussed by Daly and Guerra (2001), Podariu et al. (2003), and…”