Abstracts Colloquium November 13, 2013
Silke Britzen (MPI of Radioastronomy, Bonn, Germany)
An astronomer's view on Black Holes
Active supermassive Black Holes produce enormous amounts of energies and belong to the most luminous astrophysical objects. They are observable out to large redshifts and allow to address cosmological questions, i.e. the co-evolution of galaxies and Black Holes. Astronomers observe the most energetic emission around the central engine and trace their jets with highest resolution observations (Very Long Baseline Interferometry). Despite long-term monitoring and multi-wavelength studies of the emission processes, many questions with regard to Black Holes are still unsolved. In particular, the direct proof of their existence is still lacking. In the talk I will introduce interferometric observations, present the current observational status and introduce the most promising observational projects to test Einstein's theory of General Relativity and to obtain a snapshot of the Event Horizon.
Helvi Witek (DAMTP, Centre for Mathematical Sciences, Cambridge)
Superradiant instabilities in astrophysical systems
Black holes are key players in a wide range of fundamental physics including astrophysics as well as high energy physics. Crucial questions concern the stability properties of these fascinating objects with potentially important implications for the phase-space of solutions or the understanding of condensates in the vicinity of black holes. Of particular interest is the superradiant or "BH-bomb" like instability of Kerr BHs which arises naturally in aymptotically anti-de Sitter spacetimes or in the presence of massive fields surrounding the BH. Here, we focus on the latter scenario and present our investigations of massive fields in the vicinity of highly rotating black holes. Specifically, we have explored the time evolution of these fields with generic initial configurations and the response of the BH spacetime.
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