Image distortion in non perturbative gravitational lensing

Abstract

We introduce the idea of {\it shape parameters} to describe the shape of the pencil of rays connecting an observer with a source lying on his past lightcone. On the basis of these shape parameters, we discuss a setting of image distortion in a generic (exact) spacetime, in the form of three {\it distortion parameters}. The fundamental tool in our discussion is the use of geodesic deviation fields along a null geodesic to study how source shapes are propagated and distorted on the path to an observer. We illustrate this non-perturbative treatment of image distortion in the case of lensing by a Schwarzschild black hole. We conclude by showing that there is a non-perturbative generalization of the use of Fermat's principle in lensing in the thin-lens approximation.

22 pages, 6 figures, to appear in Phys. Rev. D (January 2001)

References in corpus (6)

• Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales
• Spacetime perspective of Schwarzschild lensing
• GR via Characteristic Surfaces
• An Exact Universal Gravitational Lensing Equation
• Image distortion from optical scalars in non perturbative gravitational lensing
• Null Cones in Schwarzschild Geometry

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• Gravitational Lensing from a Spacetime Perspective
• Classification of image distortions in terms of Petrov types
• Continuous image distortion by astrophysical thick lenses
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