Weekly Seminars for May 2009 
Wednesday 13^{th} May 2009, 4:00 P.M. Università "La Sapienza" Roma  Aula Majorana (Physics Dept., Old Building  ground floor)
Title: Kerr spacetime with an arbitrary mass quadrupole moment: geometric properties vs particle motion Abstract: An exact solution of Einstein's field equations in empty space found in 1991 by Quevedo and Mashhoon is analyzed in detail. The solution generalizes Kerr spacetime to include the case of matter with arbitrary mass quadrupole moment and is specified by three parameters, the mass M, the angular momentum per unit mass a and the mass quadrupole moment q. It reduces to the Kerr spacetime in the limiting case q=0 and to the ErezRosen spacetime when the specific angular momentum a vanishes. The geometrical properties of such a solution are investigated. Causality violations, directional singularities and repulsive effects occur in the region close to the source. Geodesic motion and accelerated motion are studied on the equatorial plane which, due to the reflection symmetry property of the solution, turns out to be also a geodesic plane. Thursday 21^{st} May 2009, 4:00 P.M. Università "La Sapienza" Roma  Aula Majorana (Physics Dept., Old Building  ground floor)
Title: Gravitational fields, generalized sigma models and quantization Abstract: In this talk I introduce the concept of generalized sigma models for which the metric of the target space depends explicitly on the coordinates of the base space. I show that several classes of gravitational fields with two commuting Killing vector fields can be represented as generalized sigma models. We explore some examples and discuss the possibility of using this new representation for analyzing the problem of canonical quantization and the calculationn of the topological spectrum of gravitational fields.
