Nonlocal gravity. Conceptual aspects and phenomenological consequences

25.05.2018 11:30 – 12:30

Even if the fundamental action of gravity is local the corresponding quantum effective action, that includes the effect of quantum fluctuations, is a nonlocal object. These nonlocalities are well understood in the ultraviolet regime but much less in the infrared, where they could in principle give rise to important cosmological effects. We summarize work of our group in which we assume that infrared effects generate a specific nonlocal term, corresponding to dynamical generation of a mass for the conformal mode. After discussing the physical motivations and conceptual aspects of this model, we study its cosmological consequences. In particular, the model generates dynamically a dark energy, its cosmological perturbations are well behaved, it fits CMB, BAO and SNa data at the same level as $\Lambda$CDM, providing a higher value of $H_0$ and a prediction for the neutrino masses, and can be distinguished from $\Lambda$CDM with future surveys such as Euclid. The model also gives distinctive predictions for gravitational waves, testable with standard sirens at LISA or the Einstein Telescope.

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Bâtiment: Ecole de Physique

Salle 234, 24 quai Ernest-Ansermet

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