Nonparametric determination of the sign of w+1 in 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 based on geometrical behaviour and is more tolerant to uncertainties of other cosmological parameters than fitting methods. It permits to distinguish between different classes of dark energy models even with relatively low precision data. We apply this method to SNLS supernovae and to gold sample of re-analyzed supernovae data from Riess et.al. 2004. Both data sets show strong indication of $w < -1$. If this result is confirmed by more extended and precise data available 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. 
Houri Ziaeepour