Gravitational lenses in arbitrary space-times

Understand

The precision reached by current and forthcoming strong-lensing observations requires to accurately model various perturbations to the main deflector.

• Hitherto, theoretical models have been developed to account for either cosmological line-of-sight perturbations, or isolated secondary lenses via the multi-plane lensing framework.
• This article proposes a general formalism to describe multiple lenses within an arbitrary space-time background.
• The lens equation, and the expressions of the amplification and time delays, are rigorously derived in that framework.