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Multiple images in gravitational lensing

  1. Jan 13, 2012 #1
    Dear all,

    so far I have only studied weak lensing. Therefore I understand little about multiple images.The light paths, by Fermat's principle, have to correspond to stationary points of the (proper) time delay. Minima, maxima saddle points. Basics are nicely reviewed here [p.14]:
    Narayan and Bartelmann 1997

    My question is why saddle points and maxima correspond to multiple images as for example claimed here [p.11]:
    Takahashi et al. 2011
    Am I right to assume that each maximum or saddle point creates two images?

    All the best,
  2. jcsd
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