Shedding light on dark energy: Theory and observations

The observed acceleration of the expansion of the Universe will be investigated. We will attempt to clarify the nature of the dark energy which is responsible for this acceleration in a project based both on theory and observations - a rather unique colla boration in Norway. Possible forms of vacuum energy will be studied in theories with extra dimensions and other models from modern elementary particle physics. The results of this theoretical attack will be systematically compared with present and future observations. In addition to understanding better the dark energy in the Universe, this approach will also test out new physics beyond the Standard Model of high energy elementary particle physics.