Physical parameter space of bimetric theory and SN1a constraints
  Bimetric theory describes a massless and a massive spin-2 field with fully
non-linear (self-)interactions. It has a rich phenomenology and has been
successfully tested with several data sets. However, the observational
constraints have not been combined in a consistent framework, yet. We propose a
parametrization of bimetric solutions in terms of the effective cosmological
constant $\Lambda$ and the mass $m_\mathrm{FP}$ of the spin-2 field as well as
its coupling strength to ordinary matter $\bar\alpha$. This simplifies choosing
priors in statistical analysis and allows to directly constrain these
parameters with observational data not only from local systems but also from
cosmology. By identifying the physical vacuum of bimetric theory these
parameters are uniquely determined. We work out the dictionary for the new
parametrization for various submodels and present the implied consistency
constraints on the physical parameter space. We then apply the dictionary to
derive observational constraints from SN1a on the physical parameters. As a
result we find that even self-accelerating models with a heavy spin-2 field are
in perfect agreement with current supernova data.
