Reconstructing the Cosmic Equation of State from Supernova distances

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  • 13 October 1999
Abstract
Observations of high-redshift type Ia supernovae indicate that the universe is accelerating, fueled perhaps by a cosmological constant or by a self-interacting scalar field. In this letter, we develop a model-independent method for estimating the form of the scalar field potential V(phi) and the associated equation of state w_(phi). Our method is based on a simple yet powerful analytical form for the luminosity distance D_L which is optimized to fit observed distances to distant extragalactic supernovae, and then differentiated to yield V(phi) and w_(phi). Our results favor w_(phi) approximately equal to -1 at the present epoch, steadily increasing with redshift. However, a cosmological constant is consistent with our results. A model-independent way of obtaining the age of the universe is also proposed.

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