Probing Cosmic Acceleration Using Model-independent Parameterizations and Three Kinds of Supernova Statistics Techniques

Abstract

Abstract In this work, we explore the evolution of the dark energy equation of state ω using Chevalliear–Polarski–Linder parameterization and binned parameterizations. For binned parameterizations, we adopt three methods to choose the redshift interval: (1) ensure that “△z = const,” where △z is the width of each bin; (2) ensure that “n△z = const,” where n is the number of SN Ia in each bin; and (3) treat redshift discontinuity points as model parameters, i.e., “free △z.” For observational data, we adopt JLA SN Ia samples, SDSS DR12 data, and Planck 2015 distance priors. In particular, for JLA SN Ia samples, we consider three statistic techniques: magnitude statistics, which is the traditional method; flux statistics, which reduces the systematic uncertainties of SN Ia; and improved flux statistics, which can reduce the systematic uncertainties and give tighter constrains at the same time. The results are as follows. For all the cases, ω = −1 is always satisfied at the 1σ confidence regions; this means that ΛCDM is still favored by current observations. For magnitude statistics, the “free △z” model will give the smallest error bars. However, this conclusion does not hold true for flux statistics and improved flux statistic. The improved flux statistic yields the largest present fractional density of matter Ω m ; in addition, this technique will give the largest current deceleration parameter q 0 , which reveals the universe with the slowest cosmic acceleration.