  Dark matter interacts gravitationally, but it presumably interacts weakly
through other channels, especially with respect to regular luminous matter. We
look at different ways in which dark matter may couple to other fields. We
briefly review some example approaches in the literature for modeling the
coupling between dark energy and dark matter and examine the possibility of an
arguably better-motivated approach via non-minimal coupling between a scalar
field and the Ricci scalar, which is necessary for renormalization of the
scalar field in curved space-time. We also show an example of a theory beyond
the Standard Model in which dark matter is uniquely connected to the inflaton,
and we use observational astrophysical constraints to specify an upper bound on
the dark matter mass. In turn, this mass constraint implies a limit on the
unification scale of the theory, a decoupling scale of the theory, and the
number of $e$-folds of inflation allowed.
