Black holes and active galactic nuclei as phenomenological test objects for a theory of quantum gravity

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The main objective of the project is to investigate the classical large-scale limit of loop quantum gravity to connect the latter theory to astrophysics and hence to observations. We are aiming towards the development of methods and techniques for a new quantum gravitational phenomenological field, where specific physical quantities can explicitly be computed. In doing so, we are able to study quantum gravity corrections in a first order large-scale approximation in dispersion relations for extragalactic high-energy radiation like TeV flares originating in active galactic nuclei. Each of the dispersion-inducing quantum gravity effects is very small, but the radiation emitted by distant astrophysical sources travels for a very long time before reaching us and can therefore be affected by a large number of such effects leading to observable results. Those effects may also be used to explain the intense short-time variability of the energy flux seen in the broadband spectra of non-thermal radiation sources like the TeV blazar PKS 2155-304. The large-scale limit allows us to find a correspondence to the black hole solutions of classical general relativity. These solutions cannot be understood only in the framework of general relativity, because the theory breaks down in the quantum domain. Hence, the description of black holes using a theory of quantum gravity, which includes all the principles of general relativity (loop quantum gravity), is necessary. Therefore, we will obtain a better understanding of black hole physics as well as of astrophysical phenomenology.