New tests of dark sector interactions from the full-shape galaxy power
  spectrum
  We explore the role of redshift-space galaxy clustering data in constraining
non-gravitational interactions between dark energy (DE) and dark matter (DM),
for which state-of-the-art limits have so far been obtained from late-time
background measurements. We use the joint likelihood for pre-reconstruction
full-shape (FS) galaxy power spectrum and post-reconstruction Baryon Acoustic
Oscillation (BAO) measurements from the BOSS DR12 sample, alongside Cosmic
Microwave Background (CMB) data from \textit{Planck}: from this dataset
combination we infer $H_0=68.02^{+0.49}_{-0.60}\,{\rm km}/{\rm s}/{\rm Mpc}$
and the 2$\sigma$ lower limit $\xi>-0.12$, among the strongest limits ever
reported on the DM-DE coupling strength $\xi$ for the particular model
considered. Contrary to what has been observed for the $\Lambda$CDM model and
simple extensions thereof, we find that the CMB+FS combination returns tighter
constraints compared to the CMB+BAO one, suggesting that there is valuable
additional information contained in the broadband of the power spectrum. We
test this finding by running additional CMB-free analyses and removing sound
horizon information, and discuss the important role of the equality scale in
setting constraints on DM-DE interactions. Our results reinforce the critical
role played by redshift-space galaxy clustering measurements in the epoch of
precision cosmology, particularly in relation to tests of non-minimal dark
sector extensions of the $\Lambda$CDM model.
