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Professor Arlie Petters
Special Joint Mathematics and Physics Colloquium
March 30, 2004
Professor Arlie Petters
Duke University
Title: Violation of the Magnification Theorem in Gravitational Lensing
One of the central issues in gravitational lensing is the growing number of observed lens systems whose image-flux-ratios violate the Local Magnification Theorem. Our talk will present the mathematical and physical aspects of this theorem, including the observational evidence for its failure.
In an attempt to reconcile theory and observations, we shall present a generalization of the local theorem to a physical Global Magnification Theorem that has weaker hypotheses. We then show how violating the global theorem yields a robust, physically realistic method for determining the presence of small-scale structures in the halos of galactic lenses. An important application of small-scale structures in the form of dark matter clumps is that their lensing action can then be used to test the Cold Dark Matter theory on galactic scales.
This talk is aimed at a diverse audience of mathematicians, physicists, and astrophysicists.