Finding structure in the dark: coupled dark energy, weak lensing, and
  the mildly nonlinear regime
  We reexamine interactions between the dark sectors of cosmology, with a focus
on robust constraints that can be obtained using only mildly nonlinear scales.
While it is well known that couplings between dark matter and dark energy can
be constrained to the percent level when including the full range of scales
probed by future optical surveys, calibrating matter power spectrum emulators
to all possible choices of potentials and couplings requires many
computationally expensive n-body simulations. Here we show that lensing and
clustering of galaxies in combination with the Cosmic Microwave Background
(CMB) is capable of probing the dark sector coupling to the few percent level
for a given class of models, using only linear and quasi-linear Fourier modes.
These scales can, in principle, be described by semi-analytical techniques such
as the effective field theory of large-scale structure.
