Momentum transfer models of interacting dark energy
  We consider two models of interacting dark energy, both of which interact
only through momentum exchange. One is a phenomenological one-parameter
extension to $w$CDM, and the other is a coupled quintessence model described by
a Lagrangian formalism. Using a variety of high and low redshift data sets, we
perform a global fitting of cosmological parameters and compare to
$\Lambda$CDM, uncoupled quintessence, and $w$CDM. We find that the models are
competitive with $\Lambda$CDM, even obtaining a better fit when certain data
sets are included.
