Probing the sources of ultrahigh-energy cosmic rays with a multi-messenger approach

Main aim of the present project is to test the longstanding suggestion that active galactic nuclei (AGN) are the acceleration sites of ultrahigh energy cosmic rays (UHECR). The solution to the question ``what are the sources of UHECRs and how are they accelerated?'' should become accessible in the near future by a combination of high-quality data of X-ray and gamma-ray satellites with UHECR observations from the Pierre Auger Observatory and limits (or observations) of high-energy neutrinos by neutr ino telescopes as Icecube. We will calculate within the present project the energy spectrum and the clustering statistics of UHECRs as well as of high-energy photons and neutrinos predicted by different AGN models, compare them to observational data of a ll three messengers and narrow thereby the variety of possible acceleration models. As a byproduct, several other topics relevant for particle physics and for astrophysics as neutrino mixing parameters, limits on violation of Lorentz invariance, relics f rom the early Universe or the strength of extragalactic magnetic fields will be investigated.