Rethinking Lensing and Λ

Strong gravitational lensing has traditionally been one of the few phenomena said to oppose a large cosmological constant; many analyses of lens statistics have given upper limits on Ω Λ that are marginally inconsistent with the concordance cosmology. Those conclusions were based on models in which the predicted number counts of galaxies at moderate redshifts ( z ~ 0.5-1) increased significantly with Ω Λ . I argue that the models should now be calibrated by counts of distant galaxies. When this is done, lens statistics lose most of their sensitivity to the cosmological constant.