This project connects two seemingly distinct areas of theoretical physics, non-perturbative quantum gravity and early universe cosmology. Using techniques the applicant has recently developed with his collaborators, nearly homogeneous universes like ours can be described as states in a full quantum gravity theory (group field theory). The effective dynamics of these universes will be calculated and compared with existing cosmological theories such as inflation, varying speed of light cosmologies, or loop quantum cosmology. The new approach has several advantages: First, the use of a certain cosmological model is motivated much better if it can be derived from a fundamental quantum gravity theory. Second, it seems quantum gravity is needed to complete the standard cosmological models, since cosmological perturbations that we see in cosmic structure today started out with wavelengths smaller than the Planck length before inflation, where quantum gravity cannot be ignored. Third, a fundamental theory of quantum gravity will provide a new picture of the beginning of space and time at the Big Bang; one possibility is that the Big Bang singularity in classical cosmology could be replaced by a phase transition from a pre-geometric quantum phase to a geometric classical phase. This would revolutionise our ideas about the origin of the universe. The project has a great potential for outreach and for attracting the public and sponsors to physics. It also has the potential to start a new line of research at the interface of quantum gravity and cosmology of which Europe will be at the forefront. The applicant brings in his experience from postdoctoral training in Germany and Canada and will receive further important training in order to establish himself as a leading figure in these new developments in Europe.
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