. I would be interested to know if in the meantime someone has produced complete pictures of the caustic
in the generic case
. Also, it would be interesting to
know how the caustic changes under a generic perturbation of the Kerr symmetry.
Some topics I would like to see discussed at the workshop:
What is the observational evidence for the existence of rotating black holes (Kerr black holes) in the universe? In particular, what is the observational evidence for the existence of a rotating black hole at the center of our galaxy?
How does the light cone issuing from a generic point in the Kerr spacetime look like? In my view, a computer-generated picture of such a light cone would very much help to understand the lensing features of a Kerr black hole. It is quite easy to produce such pictures for the Schwarzschild spacetime. Even I was able to do this, see my Living Review at http://www.livingreviews.org/lrr-2004-9. However, my attempts with the Kerr case were a complete failure. I would be interested to know if someone else, with greater computer skills, could do this.
Closely related to the preceding question: How does the caustic of a light cone
in Kerr spacetime look like? There is the excellent paper by Rauch and Blandford
[Astrophys. J. 421, 1994, 46] with a picture of the cross-section of the caustic in the extreme Kerr case . I would be interested to know if in the meantime someone has produced complete pictures of the caustic
in the generic case
. Also, it would be interesting to
know how the caustic changes under a generic perturbation of the Kerr symmetry.
Are effects of a Kerr black hole, acting as a gravitational lens, on the polarization plane of polarized light (``Gravitational Faraday Effect'') within the range of observability? What is the best mathematical formalism for describing this effect theoretically?
What is the state of the art with respect to describing lensing in a Kerr spacetime in terms of a ``lens equation''? Which is the best lens equation for this purpose? In particular, what is the advantage of an ``almost exact lens equation'', such as suggested by Virbhadra and Ellis [Phys. Rev. D 1999, 084003] for the spherically symmmetric case, over an exact treatment? (The ``almost exact lens equation'' is approximative in the sense that it assumes observer and light source in the asymptotic region and almost aligned.)
Back to the
main index
for Gravitational Lensing in the Kerr Spacetime Geometry.