IAU00458
Presentation type requested: EITHER
CONSTRAINTS ON THE COSMIC EQUATION OF STATE
V.b. Bhatia
Indira Gandhi national Open University
Recent observations of CMBR and SNe Ia support the view that the universe is flat and two-thirds of its energy density is contributed by the mysterious dark energy which has negative pressure and leads to the present phase of accelerated expansion of the universe. It obeys an equation pressure/density = w, where w >= -1. In this paper we attempt to constrain the parameter w. We use lensing statistics as a tool and adopt two approaches. First, we perform likelihood analysis of the lens surveys to constrain not only w but also the matter density parameter. We report the results of this analysis in the context of three evoltutionary models of galaxies. Second, we use the image separation distribution function of lensed quasars to constrain w by assuming that the matter density parameter lies in the observed range of ~ 0.2 - 0.4. We also comment on the formalism and point out the importance of the lens and Schechter parameters for this kind of study.
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