The team of participants is highly inhomogeneous as to individual backgrounds. We expect that for some participants the following questions may not mean anything at this stage, whereas some other participants may already be able to contribute and answer:
Q1. What is actually known about spinning lenses in the weak field regime? There is a growing literature, starting as early as 1983 (as far as we are aware of), of isolated papers, many of which do not seem to relate to each other in any straightforward way. Some of the literature appears to be contradictory at a shallow glance. We hope by the end of the workshop we should be able to unify the understanding on weak spinning lenses. Some open questions are of critical relevance. In particular: can observations distinguish a spinning dark lens from a static dark lens? Itemize.
Q2. What is already known about Kerr lensing in the strong limit? Same issues as for the weak field regime. In particular: can a Kerr lens produce Einstein rings? Itemize
Q3. Is there a direct or canonical way to relate strong field effects to weak field effects of spinning lenses?
Q4. What is NOT KNOWN about Kerr lensing? i.e.: what are actual problems that remain to be addressed? A critical question here would be whether a Kerr lens can be observationally distinguished from a non-black-hole compact object. Itemize.
Q5. What techniques are available to address the open problems? This is a question of very wide scope. We expect to un-cover and hopefully "systematize" techniques ranging from perturbative methods of mathematical rigor to issues of exact (nonperturbative, no approximation) lensing, including the recently developed spacetime-view of gravitational lensing as well as the freedom of coordinate choices for Kerr spacetime. For instance: what is the value of the unorthodox techniques as compared to traditional methods? Itemize.
It would be very valuable for all participants to read before hand a few papers that may be discussed during the workshop. It doesn't have to be a deep reading, but just enough of a reading in order to be able to contribute actively with comments or questions to the general discussion. Many papers can be freely downloaded from
http://adsabs.harvard.edu//
or from LANL at
http://xxx.lanl.gov/
Please e-mail me for details if you can't find a paper of your choice in the way it is referenced in the following list. This is a SHORT LIST. Please feel welcome to read anthing else that may have to do with the questions Q1-Q5 above. Also feel welcome to contribute by this venue other suggested reading, so long as it is essential to the discussion:
1. Rauch and Blandford 1994, Astrophysical Journal 421, 46-68
2. Sereno 2003, astro-ph/0307243
3. Bozza 2002, gr-qc/0210109
4. Vazquez and Esteban 2004, gr-qc/0308023
5. Reynolds and Nowak, astro-ph/0212065
For newcomers to the field of gravitational lensing, an understanding (even shallow) of static lenses is probably necessary. The standard text reference for the physically inclined is
Ehlers, Falco and Schneider, "Gravitational Lenses"
and the text for the mathematically inclined is
Petters, Levine and Wambsganss, "Singularity theory and gravitational lensing"
There are also the Living Reviews in Relativity of J Wambsganss (gravitational lensing for the astronomically inclined) and of Volker Perlick (spacetime-view of gravitational lensing for the general-relativity inclined). These can be downloaded freely from
http://www.livingreviews.org/
Participants who are not already familiar with the literature of the strong regime of static lenses may want to read Bozza 2002, gr-qc/0208075.
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