My research is in the areas of theoretical astroparticle physics and cosmology. In particular, it revolves around weakly interacting particles (neutrinos, the hypothetical axion, or weakly interacting dark matter candidates), their role in astrophysics and cosmology, and conversely, what we can learn about their properties from astrophysical and cosmological arguments and observations. One of my specialities is supernova neutrinos and neutrino oscillations in dense media.