all projects tagged structures

Information entropies (like Kullback-Leibler or Rényi entropies) are measures of statistical randomness of distributions, if applied to the posterior of a distribution they serve as a quantification of remaining statistical uncertainty, i.e. how well measurements have been able to improve the knowledge on a given physical model. We work on the connection between more conventional tools in statistics and inference such as likelihoods and statistical tests, with novel concepts like information entropies, with an application to cosmological data sets.

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.

Modern cosmology is a statistical science and we are interested in questions related to the information content of large-scale structure surveys, in particular in the nonlinear regime, selection of models and the effect of systematical errors on the parameter estimation and model selection process. In particular, we investigate what properties about gravity are in principle knowable from cosmological surveys, how non-Gaussian structures can be described in an efficient way and how information about fundamental physics can be extracted from non-Gaussian structures.