Model-independent analysis of dark energy: supernova fitting result

This paper uses supernova data to explore the property of dark energy by some model-independent methods. We first Taylor expand the scale factor a (t) and the luminosity distance d(L) to the fifth order to find that the deceleration parameter q(0) < 0. This result just invokes the Robertson-Walker metric. So the conclusion that the universe is expanding with acceleration is more general. Then we discuss several different parametrizations used in the literature. We also propose two modified parametrizations. We find that omega(DEO) is less than - 1 almost at 1 sigma level from all the parametrizations used in this paper. We also find that the transition redshift from deceleration phase to acceleration phase is z(T) similar to 0.3.