Aleksander Chatrchyan (DESY), The Stochastic Relaxion

Tuesday 27 Jun 2023, 14:00 → 15:30 Europe/Stockholm

Albano 3: 6228 - Mega (22 seats) (Albano Building 3)

Light scalar fields, such as axions, can play an important role in cosmology. In this talk I will discuss the mechanism of cosmological relaxation of the electroweak scale, which provides a dynamical solution to the Higgs mass hierarchy problem. In the simplest model, the Higgs mass is scanned during inflation by a light field, the (rel)axion, whose slow-roll dynamics selects a naturally small Higgs vev. We revisit the original proposal and investigate the mechanism in a regime where the relaxion is subject to large fluctuations. We investigate the role of fluctuations for transitions between the local minima of the potential and derive a new stopping condition for the field. We investigate the consequences both for the QCD relaxion and the strong CP problem, as well as for non-QCD models. We identify a new region of the parameter space where the stochastic misalignment of the relaxion from its local minimum due to fluctuations can naturally explain the observed dark matter density in the universe.