Image separation vs. redshift of lensed QSOs: Implications for galaxies and Λ

The average observed image separation of multiply-imaged QSOs decreases sharply with source redshift. Such a relation cannot be reproduced in any plausible cosmological model if the lens-galaxy mass distribution is assumed to be a power law, and/or the scaling laws of the lens-galaxy population are those of ellipticals. It is shown here that the observed relation, which is due to the lack of wide separation high redshift QSOs, arises naturally if galaxies have changing logarithmic density profiles, and if the scaling laws of the lensing galaxy population are those of spirals.