Gravitational tests of electroweak relaxation
  We consider a scenario in which the electroweak scale is stabilized via the
relaxion mechanism during inflation, focussing on the case in which the
back-reaction potential is generated by the confinement of new strongly
interacting vector-like fermions. If the reheating temperature is sufficiently
high to cause the deconfinement of the new strong interactions, the
back-reaction barrier then disappears and the Universe undergoes a second
relaxation phase. This phase stops when the temperature drops sufficiently for
the back-reaction to form again. We identify the regions of parameter space in
which the second relaxation phase does not spoil the successful stabilization
of the electroweak scale. In addition, the generation of the back-reaction
potential that ends the second relaxation phase can be associated to a strong
first order phase transition. We then study when such transition can generate a
gravitational wave signal in the range of detectability of future
interferometer experiments.
