ROMFORSK-Program for romforskning

One of the most outstanding problems in physics and astrophysics today is the existence of dark energy, which is inferred from the apparent accelerated expansion of the universe. Dark energy is believed to comprise about 70% of the energy content of the u niverse today, however, it's nature is largely unknown. The simplest model is to assume that the dark energy is in the form of a cosmological constant. There are, however, good reasons to believe that the nature of the dark energy could be more complicate d than this. In this project we will study a family of models where dark energy is a scalar field that couples to either cold dark matter, baryons or neutrinos. The nature and value of neutrino masses are other important problems in today's physics. Neu trinos are known to possess a small mass, but the limits on the absolute scale on neutrino mass are still poor. The best limits on neutrino mass today come from cosmology, however there have been identified strong degeneracies between neutrino mass and da rk energy parameters, especially for the coupled models. Euclid is a proposed ESA M-class mission with a targeted launch in 2018. Its primary objective is to study dark energy, and the neutrino mass is one of the secondary objectives of the experiment. The main observational targets will be baryonic acoustic oscillations, and weak lensing measurements. In this proposal we will study the above models, emphasizing the use of the matter power spectrum and its ability when it comes to constraining the dar k energy models and massive neutrinos. There are good reasons to believe that the achievements of the experiment could be different when confronted with our concrete, physical models, than when constraining the simplest, observationally based dark energy parameters. This project also covers the organizational part of the Norwegian Euclid participation, including industrial relations and preparations for a segment of the Euclid Science Data Centres in Oslo.