Probing Cosmic Acceleration by Using Model-Independent Parametrizations and Three Kinds of Supernova Statistics Techniques

Abstract

In this work, we explore the evolution of the dark energy equation of state ω by using Chevalliear-PolarskiLinder (CPL) parametrization and the binned parametrizations. For binned parametrizations, we adopt three methods to choose the redshift interval: I. Ensure that "Δz = const", where Δz is the width of each bin; II.Ensure that "nΔz = const", where n is the number of SNIa in each bin; III. Treat redshift discontinuity points as models parameters, i.e. "free Δz". For observational data, we adopt JLA type Ia supernova (SNIa) samples, SDSS DR12 data, and Planck 2015 distance priors. In particular, for JLA SNIa samples, we consider three statistic techniques: I. Magnitude statistics, which is the traditional method; II. Flux statistics, which reduces the systematic uncertainties of SNIa; III. Improve flux statistics, which can reduce the systematic uncertainties and give tighter constrains at the same time. The results are as follows: (1) For all the cases, ω = -1 is always satisfied at 1σ confidence regions; It means that ΛCDM is still favored by current observations. (2) For magnitude statistics, "free Δz" model will give the smallest error bars; this conclusion does not hold true for flux statistics and improved flux statistic. (3) The improved flux statistic yields a largest present fractional density of matter Ωm; in addition, this technique will give a largest current deceleration parameter q0 , which reveals a universe with a slowest cosmic acceleration.

10 pages, 8 figures and 3 tables. arXiv admin note: text overlap with arXiv:1708.03143

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