Nonparametric determination of the equation of state of Dark Energy
We present a nonparametric method to determine the sign of w + 1 in the equation of state of dark energy. It is more tolerant to uncertainties of other cosmological parameters than fitting methods, and permits to distinguish between different classes of dark energy models even with relatively low resolution data. We apply this method to SNLS supernovae and to gold sample of re-analyzed supernovae data from Riess et al.2004 [1]. Both data sets show strong indication of w < −1. If this result is confirmed by more extended and precise data avalable in near future, many of dark energy models, including simple cosmological constant, standard quintessence models without interaction between quintessence scalar field(s) and matter, and scaling models are ruled out. Recent observations of SuperNovae (SN), Cosmic Microwave Background (CMB), and Large Scale Structures (LSS) indicate that the dominant content of the Universe is a mysterious energy with an equation of state very close to Einstein Cosmological Constant. The equation of state is defined by w, the ratio of pressure p to density ρ, w = P/ρ. For a cosmological constant w = −1. The observed mean value of w for dark energy is very close to −1. Some of the most recent estimations are the followings: From combination of 3-year WMAP and SuperNova Legacy Survey (SNLS), w = −0.97