Time delay in gravitational lens systems and cosmological parameters

Abstract. The time delay between the multiple images in gravitational lens systems is affected by large scale mass distribution in the lens, even though it might not have observable effects on the macro images. Inhomogeneity at very small scale will not directly affect the time delay but will influence the models of mass distribution in the lens galaxy. How this degeneracy can be eliminated is described. A method to determine time delay based on smoothed cubic splines is explained. The value of the Hubble Constant, inferred from the time delay in 5 well-constrained lens systems is 56 ± 8 kIn S-1 Mpc-1