Signatures from Dark Matter Accretion and Superradiance in Black Hole Ringdown

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Black hole ring down is, potentially, one of the cleanest observables to be extracted from gravitational wave production from a gravitational collapse event. It is will described in terms of linear perturbation theory and has a number of key features that allow it to be used as a probe of new physics. In this project we plan to characterize the impact on ring down from a range of different effects. The main focus will be on studying the impact of dark matter accretion around a black hole by developing a numerical algorithm that combines an N-body code with a numerical relativity code. There will be a number of technical challenges - how to smooth the energy density of the n-body system, how to accurately define the initial conditions, how to identify the relevant time scales - but, from the first step it should be possible to construct a novel, working tool for studying such systems. With the tool in hand, one can then simulate the dark matter halos around black holes and look for potentially interesting signatures, most notable the impact such halos will have on mergers and the resulting ringdown signal.A second focus will be to model the superradiance from spin 2 fields around a Kerr black hole. It has been shown that higher spin fields enter the super-radiant regime much more efficiently than scalar fields. This means that it should be possible to simulate theses systems much more quickly on a computer and watch the onset of super-radiance. Once this is shown to be true, it should be possible to study the possible onset of super-radiance around binary systems and their backreaction on mergers. Again, the focus will be on how such a process affects ringdown.Finally, it is essential to come up with accurate methods to extract information from the ringdown signal. A final focus will be to develop such methods that can be applied to current and future data.