[Seminars] EFI Colloquium Today!

[Holly Jaffey]

EFI COLLOQUIUM TODAY!

Monday April 9, 2018
PRC 201
4:15pm
Reception following

Speaker:  Christof Wetterich (University of Heidelberg)

Title:   Scale symmetry in particle physics and cosmology
Abstract: Scale symmetry can be a central ingredient in cosmology. It arises from fixed points of running couplings in quantum gravity - no intrinsic mass or length scales are present anymore. Such a world can be realised in the infinite past and future of our Universe.
The ultraviolet fixed point makes quantum gravity asymptotically safe and non-perturbatively renormalizable. Successful predictions, as for the mass of the Higgs boson, are related to the behavior of couplings close to the fixed point. The approximate scale invariance close to the fixed point is reflected in cosmology in the almost scale invariant spectrum of the observed primordial cosmic fluctuations. The approach to the infrared fixed point in the asymptotic future is characterized by the dynamics of an almost massless cosmon - the pseudo Goldstone boson of spontaneously broken scale symmetry. It is responsible for dynamical dark energy.
Both inflation and the present dynamical dark energy arise from the same scalar field. The history of the Universe describes a crossover from a “past fixed point“ where all particles are massless, to a “future fixed point“ where exact scale invariance is spontaneously broken, generating the particle masses. The cosmological solution can be extrapolated to the infinite past in physical time - the Universe has no beginning and no physical singularity.  A simple model is compatible with all present cosmological observations. It could be tested by the observation of huge lumps in the cosmic neutrino background, the detection of early dark energy , or rather large primordial graviton fluctuations generated during inflation.
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