The role of Lambda in the cosmological lens equation

Understand

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 can not be accounted for by a proper use of angular diameter distances, are derived.
• First, a term 2m b Lambda/3 has to be added to the bending angle, where "m" is the lens mass and "b" the impact parameter.