Invited seminars

Dilaton Inflation and the Dynamical Origin of the Planck Scale

by Kai Schmitz

Europe/Brussels
Description

Classical scale invariance represents a promising framework for model building beyond the Standard Model. However, once coupled to gravity, any scale-invariant microscopic model requires an explanation for the origin of the Planck scale. In this talk, I will present a minimal example for such a mechanism and show how the Planck mass may be dynamically generated in a strongly coupled gauge sector. I will consider the case of hidden SU(N) gauge interactions that link the Planck scale to the condensation of a scalar bilinear operator that is nonminimally coupled to curvature. The effective theory at energies below the Planck mass contains two scalar fields: the pseudo-Nambu-Goldstone boson of spontaneously broken scale invariance (the dilaton) and a gravitational scalar degree of freedom that originates from the R^2 term in the effective action (the scalaron). I will discuss the effective potential for the coupled dilaton-scalaron system at one-loop order and demonstrate that it can be used to successfully realize a stage of slow-roll inflation in the early Universe. Remarkably enough, the resulting predictions for the primordial scalar power spectrum include and extend those of standard R^2 inflation. For comparatively small coupling constants in the gravitational sector, one obtains a spectral index n_s ~ 0.97 and a tensor-to-scalar ratio as large as r ~ 0.08. This talk is based on work in progress in collaboration with Jisuke Kubo, Manfred Lindner und Masatoshi Yamada

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