Constraints on Cosmic Equation of State from Joint Analysis of Standard Rulers and Standard Candles

Abstract

A key issue of contemporary cosmology is the problem of currently accelerating expansion of the Universe. The nature of this phenomenon is one of the most outstanding problems of physics and astronomy today. Its origin may be attributed to either unknown exotic material component with negative pressure — so-called Dark Energy (DE), to infra red modification of gravity at cosmological scale or requires to relax the assumption of homogeneity of the Universe. The strength of modern cosmology lies in consistency across independent pieces of evidence (like e.g. CMB anisotropies, the large-scale distribution of galaxies, the observed abundances of light elements, etc.) rather than in single one, crucial experiment. In this spirit we performed a joint analysis of two dark energy models using five different tests. These tests will be called diagnostics and include the data coming from supernovae, Gamma Ray Bursts, CMB acoustic peaks, Baryon Acoustic Oscillations and strong lensing systems. Part of the diagnostics makes use of the angular diameter distance, and part of them uses the luminosity distance splitting these probes into two categories: Standard Rules and Standard Candles. It was shown that combined analysis of them had higher restrictive power in the parameter space. The best fits we obtained for the model parameters in joint analysis turned out to prefer cases effectively equivalent to CDM model. Our findings are in agreement with paralel studies performed by other authors on different sets of diagnostic probes.