Abstract
If the light emitted by a source is deflected by a single matter concentration in the universe, the theory for a single geometrically-thin mass distribution as developed in Chap. 5 applies. However, one can easily imagine situations where the light is deflected several times on the way from the source to the observer. For example, a distant QSO might be lensed by two galaxies at quite different redshifts; in particular, in the spectra of high redshift QSOs, one often finds absorption lines which correspond to intervening matter at several redshifts. If the absorbing matter forms part of a sufficiently large mass concentration (e.g, a galaxy), the multiple absorption lines could indicate that the light from the QSO is deflected more than once. In addition, microlensing need not be confined to objects at a single redshift. Furthermore, if the clumpy universe described in Chap. 4 does approximate the matter distribution in our universe, clumps at all redshifts will influence light propagation. We describe numerical studies of this process in a later chapter. As it turns out, the multiple lens-plane theory ([BL86.1], [KO87.5]) is very convenient for the study of light rays (and bundles) through a clumpy universe.
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© 1992 Springer-Verlag New York Inc.
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Schneider, P., Ehlers, J., Falco, E.E. (1992). Multiple light deflection. In: Gravitational Lenses. Astronomy and Astrophysics Library. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-2756-4_9
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DOI: https://doi.org/10.1007/978-1-4612-2756-4_9
Publisher Name: Springer, New York, NY
Print ISBN: 978-1-4612-7655-5
Online ISBN: 978-1-4612-2756-4
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