Role of lambda in the cosmological lens equation.
The cosmological constant Lambda affects cosmological gravitational lensing. Effects due to Lambda 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 deltaalpha[over ;]_(Lambda)=2mbLambda/3 has to be added to the bending angle, where m is the lens mass and b the impact parameter. Second, Lambda brings about a difference in the redshifts of multiple images. Both effects are quite small for real astrophysical systems, deltaalpha[over ;]_(Lambda) less, similar1muarcsec and Deltaz_(s) less, similar10(-7).
Sereno
Mauro
M
Institut für Theoretische Physik, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. sereno@physik.unizh.ch