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Beyond the Thin Lens Approximation

Ted Pyne·Mark Birkinshaw
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Abstract

We obtain analytic formulae for the null geodesics of Friedmann-Lema\^ıtre-Robertson-Walker spacetimes with scalar perturbations in the longitudinal gauge. We use these to provide a rigorous derivation of the cosmological lens equation. We obtain an expression for the magnification of a bundle of light rays in these spacetimes without restriction to static or thin lens scenarios. We show how the usual magnification matrix naturally emerges in the appropriate limits.

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Ted Pyne, Mark Birkinshaw. 1994-05-10. Beyond the Thin Lens Approximation. https://arxiv.org/abs/astro-ph/9405021

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