Complementarity of Neutrinoless Double Beta Decay and Cosmology
  Neutrinoless double beta decay experiments constrain one combination of
neutrino parameters, while cosmic surveys constrain another. This
complementarity opens up an exciting range of possibilities. If neutrinos are
Majorana particles, and the neutrino masses follow an inverted hierarchy, then
the upcoming sets of both experiments will detect signals. The combined
constraints will pin down not only the neutrino masses but also constrain one
of the Majorana phases. If the hierarchy is normal, then a beta decay detection
with the upcoming generation of experiments is unlikely, but cosmic surveys
could constrain the sum of the masses to be relatively heavy, thereby producing
a lower bound for the neutrinoless double beta decay rate, and therefore an
argument for a next generation beta decay experiment. In this case as well, a
combination of the phases will be constrained.
