Abstracts Colloquium November 7, 2012

Wolfram Schmidt (University of Göttingen)

From Kepler ellipses to zoom whirls

Kepler's third law for the motion of planets around the Sun can readily be derived via the Hamilton-Jacobi method (also know as action-angle variable formalism). This method is very powerful for systems with phase-space trajectories that can be decomposed into periodic motions. The generalization of the Hamilton-Jacobi derivation of Kepler's third law to the geodesic motion of test bodies in Schwarzschild spacetime is straight-forward and works even for Kerr spacetime if certain symmetries are fulfilled. Although the orbital motion is generally aperiodic in the relativistic case (the prediction of the perihelion drift of Mercury was the first test of general relativity), it is fully determined by three fundamental frequencies, which are integrals of motion corresponding to the radial, angular, and azimuthal degrees of freedom. The fundamental frequencies can be calculated even for the most extreme orbits in Kerr spacetime (for example, "zoom-whirls"), which do not even remotely resemble Newtonian elliptical orbits. The corresponding time scales are relevant for the secular changes of geodesic orbits due to the emission of gravitational radiation, for example, for low-mass objects in close orbits around supermassive black holes.

Bernd Heber (Universitaet Kiel)

Energetic particles in the Heliosphere

The heliosphere is the region around the Sun that is filled by the solar wind and its embedded magnetic field. The interaction of the supersonic solar wind with the local interstellar medium leads to a transition from supersonic to subsonic speeds at the heliospheric termination shock. The latter is regarded to be the source of the anomalous component of cosmic rays. Within the heliosphere "local" energetic particle sources, like the Sun and interplanetary shock waves contribute to the cosmic ray flux, too. At energies below a few GeV the observed galactic and anomalous cosmic ray intensities are modulated by the heliospheric magnetic field. In my contribution, both the current knowledge and hypotheses about modulation and the transport of cosmic rays in the heliosphere are reviewed.

Betti Hartmann (Jacobs University Bremen)

Holographic superconductors and superfluids

Recently, the gauge/gravity duality has been used to describe so-called holographic superconductors and superfluids with the help of black holes and solitons in Anti-de Sitter (AdS) space-time. The basic idea here is the duality between a weakly coupled gravity theory in a space-time with negative cosmological constant (i.e. a AdS space-time) and a strongly coupled Quantum Field theory that "lives" on the conformal boundary of AdS. In the first part of the talk, I will discuss the basic approach and point out that a number of the qualitative features of these models are in good agreement with experimental results. In the second part, I will discuss holographic superconductors and superfluids away from the probe limit, i.e. taking backreaction of the space-time into account.

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