The Light Radion Window
  Inspired by the Contino-Pomarol-Rattazzi mechanism we explore scenarios with
a very light (100 keV to 10 GeV) radion which could be associated with the
suppression of the electroweak contribution to vacuum energy. We construct
explicit, realistic models that realize this mechanism and explore the
phenomenological constraints on this class of models. Compared with axion-like
particles in this mass range, the bounds from SN 1987a and from cosmology can
be much weaker, depending on the the mass of the radion and its coupling to
other particles. With couplings suppressed by a scale lower than 100 TeV much
of the mass window from 100 keV to 10 GeV is still open.
