all projects tagged perturbations

Axions and axion-like particles are an interesting alternative to dark matter on the TeV-scale and should show new phenomena on small scales. Their very light masses cause their wave function to have de Broglie-wavelengths comparable to the size of cosmological objects such as dwarf galaxies, with less substructure on small scales and a density core as a natural consequence. With T. Schwetz-Mangold (KIT) and J. Jaeckel (Heidelberg) we are investigating signatures of axion dark matter. This requires to do quantum mechanics in gravitational fields and find analogues to classical concepts like gravitational collapse or virialisation for quantum mechanical, self-gravitating systems.

Cosmic inflation is an early phase of accelerated expansion that solves the flatness-problem in FLRW-cosmologies and is a mechanism for introducing fluctuations in the distribution of matter. Of particular interest to us are inflationary non-Gaussianities and their measurement in future large-scale structure surveys. The best way of measuring higher-order non-Gaussianities is still unclear; while there is a clear way of computing polyspectra from covariant perturbation theory, their estimation from data quickly becomes a combinatorial problem, for which we use advanced sampling methods.