Theoretical Physics of the Early Universe

Evolution of the lepton asymmetry Y over temperature T (z=M/T, M is the mass of a decaying heavy neutrino). The final asymmetry is the sum over the solid lines for large z. For the top panel, the decay of quantum mechanical flavour coherence (dashed) is not taken into account, for the bottom panel, it is. The paper can be found here.

This group performs research at the interface of Theoretical Particle Physics and Cosmology.

The Universe as we observe it today is the result of a number of non-equilibrium Particle Physics processes that have occurred during its history. Small density perturbations have collapsed into galaxies and clusters, because after recombination, the coupling between individual baryons has become too weak in order to keep these in an equilibrium state. The freeze-out of Dark Matter is a non-equilibrium process as well. Furthermore, a deviation from thermal equilibrium is a necessary condition for the generation of the asymmetry between matter and antimatter in the Universe.

A viable explanation for the generation of primordial density perturbations that have eventually grown into galaxies and clusters is the amplification of quantum fluctuations in the expanding space-time, which can be described by Quantum Field Theory in curved space times.

We develop theoretical methods of describing High-Energy Particle Physics processes in a finite-density, non-equilibrium background and in curved space times. These techniques are applied to specific scenarios for generating the matter-antimatter asymmetry and the seed of structure in the Universe.

We are cooperating and collaborating with other groups working on Theoretical Particle Physics at TUM. Information on these groups, joint activities, open positions and for visitors is available here.