Title: Constraints on the Inner Cluster Mass Profile and the Power Spectrum Normalization from Strong Lensing Statistics

Abstract: Strong gravitational lensing is a useful probe of both the intrinsic properties of the lenses and the cosmological parameters of the universe. The large number of model parameters and small sample of observed lens systems, however, have made it difficult to obtain useful constraints on more than a few parameters from lensing statistics. Here we examine how the recent WMAP measurements help improve the constraining power of statistics from the radio lensing survey JVAS/CLASS. We find that the absence of theta>3'' lenses in CLASS places an upper bound of beta<1.25 (1.60) at 68% (95%) CL on the inner density profile, rho \propto r^{-beta}, of cluster-sized halos. Furthermore, the favored power spectrum normalization is sigma_8 >= 0.7 (95% CL). We discuss two possibilities for stronger future constraints: a positive detection of at least one large-separation system, and next-generation radio surveys such as LOFAR.