all projects tagged gravity

We work on the design of tests of specific, non-standard tests of gravity on galactic scales like screening-mechanisms. Furthermore, we investigate possible signatures of post-Newtonian gravity in cosmological surveys, and how general relativistic effects can be observed in cosmology.

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.

Constructive gravity asserts that there is a clear path of constructing a gravitational interaction for particles that is determined completely by their non-gravitational interactions. Our group works in cooperation with F.P. Schuller (Erlangen) and M.C. Werner (Kyoto) on cosmological tests of constructive gravity, and we work on astrophysical and cosmological applications of area-metric gravity, as well as on its conceptual construction.

Spherical collapse of a halo is one of the few instances where the fully nonlinear, relativistic equations of motion can be solved. In particular, our group has worked on collapse in non-standard gravitational models and computed the influence of tidal shear fields, split up into shear and vorticity, on the collapse dynamics. The overdensity needed for spherical collapse allows the prediction of number densities of expected haloes in a cosmic volume, and constraints on cosmological parameters as well as on the gravitational interaction from that quantity.