Abstract

The cosmological constant Λ affects cosmological gravitational lensing. Effects due to Λ can be studied in the framework of the Schwarzschild–de Sitter spacetime. Two novel contributions, which cannot be accounted for by a proper use of angular diameter distances, are derived. First, a term δα̂Λ=2mbΛ/3 has to be added to the bending angle, where m is the lens mass and b the impact parameter. Second, Λ brings about a difference in the redshifts of multiple images. Both effects are quite small for real astrophysical systems, δα̂Λ≲1μarcsec and Δzs≲10-7.