Key points are not available for this paper at this time.
Gravitational lensing directly measures mass density fluctuations along the lines of sight to very distant objects. No assumptions need to be made concerning bias, the ratio of fluctuations in galaxy density to mass density. Hence, lensing is a very useful tool for studying the universe at low to moderate redshifts.
Wambsganß et al. (Tue,) studied this question.
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