Marcus C. Werner, Kyoto University
(Hakubi Assistant Professor, Yukawa Institute for Theoretical Physics)


Title:
New light on gravitational optics

Abstract:
Light remains our richest source of information about the distant universe,
and the influence of gravity upon it plays an important role in astronomy. In
this talk, I will begin by reviewing aspects of gravitational lensing theory, in
particular the notion of magnification, and describe the recent identification
of the first strongly lensed type Ia supernova (with Robert Quimby et al.),
which also provided the first direct measurement of this quantity. Then I will
report on recent theoretical work (with Amir Aazami) that derives a generalization
of this quantity from the standard approximation used in lensing to arbitrary convex
normal neighbourhoods of Lorentzian spacetimes, by means of the van Vleck determinant
and the exponential map, in view of possible lensing tests of modified theories.
Finally, after touching upon ongoing work regarding gravitational optics in Lorentz-
violating theories, I will present some unpublished correspondence of Einstein
which draws attention to a historical, and largely forgotten, optical test of
Lorentz invariance.