Beschreibung:
<jats:p>Quantitative estimates of lensing probabilities must be self-consistent. In particular, for asymptotically isothermal models: (1) using the (3/2)<jats:sup>1/2</jats:sup> correction for the velocity dispersion overestimates the expected number of lenses by 150% and their average separations by 50%, thereby introducing large cosmological errors; (2) when a core radius is added to the SIS model, the velocity dispersion must be increased; and (3) cross sections and magnification bias cannot be separated when computing the lensing probability. When we self-consistently calculate the effects of finite core radii in flat cosmological models, we find that the cosmological limits are independent of the core radius.</jats:p>