  We discuss a mechanism which generates a mass term for a scalar field in an
expanding universe. The mass of this field turns out to be generated by the
cosmological constant and can be naturally small if protected by a conformal
symmetry which is however broken in the gravitational sector. The mass is
comparable today to the Hubble time. This scalar field could thus impact our
universe today and for example be at the origin of a time variation of the
couplings and masses of the parameters of the standard model.
