Particle Cosmology is an interdisciplinary field of fundamental research, which very fruitfully interfaces to high energy physics, astroparticle physics, general relativity and early Universe physics. It currently addresses very distinct and fundamental problems of our present understanding of the structure of the Universe: the nature of Dark Matter and its embedding in models beyond the Standard Model of particle physics, the creation of a matter-antimatter asymmetry, the explanation of the presence of Dark Energy and the implementation of an early inflationary phase. These questions are of course related to the high energy completion of the Standard Model and so to string theory on one side, and to particle physics phenomenology on the other.

Dark Matter

An attractive Dark Matter candidate is the gravitino, the superpartner of the graviton in extensions of the Standard Model including supersymmetry. At DESY a model for quasi stable gravitinos has been developed which leads to a consistent cosmology including leptogenesis, primordial nucleosynthesis and dark matter in the right abundance. In the near future several predictions of the model will be tested at LHC and the Fermi Gamma-ray Space Telescope. Important signatures at LHC and ILC are coming from various next-to-lightest superparticles, such as scalar tau, scalar top, scalar neutrino or higgsino. Measuring the properties of those particles and determining the gravitino mass could lead us to determine the nature of the supersymmetry breaking mediation and also its breaking mechanism.

Baryogenesis

In the DESY theory group detailed studies have been carried out on the connection between neutrino properties and matter-antimatter asymmetry in the scenario of baryogenesis via leptogenesis. The conceptual and quantitative aspects of leptogenesis are still under study with the goal of achieving a full quantum mechanical description beyond the classical approach based on the Boltzmann equation.

Dark Energy and Inflation

Inflation, a likely phase of exponential expansion of the universe, provides a successful description of the initial conditions for the present state and of the cosmic microwave background data. However many conceptual problems are still unsolved, especially in the embedding of inflation in wider particle physics models beyond the Standard Model. Dark Energy is also a very open question and it is still unclear if it can be explained by a pure cosmological constant or by a dynamical field.

The group is supported by the German Science Foundation (DFG) through a Collaborative Research Center Sonderforschungsbereich 676 on Particles, Strings and the Early Universe.

Some suggested lecture notes for further reading: