Interacting dark energy from redshift-space galaxy clustering
  Interacting dark energy models have been proposed as attractive alternatives
to $\Lambda$CDM. Forthcoming Stage-IV galaxy clustering surveys will constrain
these models, but they require accurate modelling of the galaxy power spectrum
multipoles on mildly non-linear scales. In this work we consider a dark
scattering model with a simple 1-parameter extension to $w$CDM - adding only
$A$, which describes a pure momentum exchange between dark energy and dark
matter. We then provide a comprehensive comparison of three approaches of
modeling non-linearities, while including the effects of this dark sector
coupling. We base our modeling of non-linearities on the two most popular
perturbation theory approaches: TNS and EFTofLSS. To test the validity and
precision of the modelling, we perform an MCMC analysis using simulated data
corresponding to a $\Lambda$CDM fiducial cosmology and Stage-IV surveys
specifications in two redshift bins, $z=0.5$ and $z=1$. We find the most
complex EFTofLSS-based model studied to be better suited at both, describing
the mock data up to smaller scales, and extracting the most information. Using
this model, we forecast uncertainties on the dark energy equation of state,
$w$, and on the interaction parameter, $A$, finding $\sigma_w=0.06$ and
$\sigma_A=1.1$ b/GeV for the analysis at $z=0.5$ and $\sigma_w=0.06$ and
$\sigma_A=2.0$ b/GeV for the analysis at $z=1$. In addition, we show that a
false detection of exotic dark energy up to 3$\sigma$ would occur should the
non-linear modelling be incorrect, demonstrating the importance of the
validation stage for accurate interpretation of measurements.
