Exact solutions and their interpretation

This is the account of the workshop Exact solutions and their interpretation at the 16-th International Conference on General Relativity and Gravitation held in Durban, July 15-21, 2001. Work reported in 32 oral contributions spanned a wide variety of topics, ranging from exact radiative spacetimes to cosmological solutions. Two invited review talks, on the role of exact solutions in string theory and in cosmology, are also described.Comment: 18 pages. To be published in: Proceedings of the 16th International Conference on General Relativity and Gravitation, Durban, 15 - 21 July, 2001, eds. N.T. Bishop and S.D. Maharaj, World Scientifi

Rotating charged black holes accelerated by an electric field

The Ernst method of removing nodal singularities from the charged C-metric representing uniformly accelerated black holes with mass $m$, charge $q$ and acceleration $A$ by "adding" an electric field $E$ is generalized. Utilizing the new form of the C-metric found recently, Ernst's simple "equilibrium" condition $mA=qE$ valid for small accelerations is generalized for arbitrary $A$. The nodal singularity is removed also in the case of accelerating and rotating charged black holes, and the corresponding equilibrium condition is determined.Comment: 6 pages, 1 figur

Gravitational waves propagating into Friedmann--Robertson--Walker universes

We consider space-times with two isometries which represent gravitational waves with distinct wavefronts which propagate into exact Friedmann-Robertson-Walker (FRW) universes. The geometry of possible wavefronts is analysed in detail in all three types of FRW models. In the spatially flat and open universes, the wavefronts can be planar or cylindrical; in the closed case they are toroidal. Exact solutions are given which describe gravitational waves propagating into the FRW universes with a fluid with a stiff equation of state. It is shown that the plane-fronted waves may include impulsive or step (shock) components, while the cylindrical waves in the spatially flat and open universes and the toroidal waves in closed universes may contain steps. In general, wavefronts may exist which have an arbitrary finite degree of smoothness. In all cases, the waves are backscattered. The head-on collision of such waves is also briefly mentioned.Comment: 26 pages, LaTeX, 8 figures not included. To be published in the November issue of Annals of Physic

Light Deflection in Plasma in the Hartle-Thorne Metric and in Other Axisymmetric Spacetimes with a Quadrupole Moment

The light propagation in plasma medium around stationary gravitating objects is studied in the geometrical optics limit. Static metrics with quadrupole moments are considered, however, the main attention is paid to the stationary Hartle-Thorne metric and Kerr metric. Their different effects on the light deflection are compared. The deflection angle is given in a general analytic form, the detailed calculations are performed in the weak field limits and illustrated graphically. The trajectories of the light rays are constructed and compared, emphasizing the role of the quadrupole moment.Comment: accepted in Phys Rev

Quantum Detection of Conicity

We investigate the sensitivity of an Unruh-DeWitt detector to the global features of a deficit angle that are otherwise classically inaccessible. Specifically, we consider a detector placed inside an infinite thin hollow cylinder whose spacetime is everywhere flat but outside of which the spacetime has a deficit angle and study its response to a scalar field to which it couples. We find that the response of the detector is sensitive to the deficit angle, despite the fact that it does not interact with the cylinder.Comment: 5+1 pages, 4 figure