Listening to the sound of dark sector interactions with gravitational
  wave standard sirens
  We consider two stable Interacting Dark Matter -- Dark Energy models and
confront them against current Cosmic Microwave Background data from the
\textit{Planck} satellite. We then generate luminosity distance measurements
from ${\cal O}(10^3)$ mock Gravitational Wave events matching the expected
sensitivity of the proposed Einstein Telescope. We use these to forecast how
the addition of Gravitational Wave standard sirens data can improve current
limits on the Dark Matter -- Dark Energy coupling strength ($\xi$). We find
that the addition of Gravitational Waves data can reduce the current
uncertainty by a factor of $5$. Moreover, if the underlying cosmological model
truly features Dark Matter -- Dark Energy interactions with a value of $\xi$
within the currently allowed $1\sigma$ upper limit, the addition of
Gravitational Wave data would help disentangle such an interaction from the
standard case of no interaction at a significance of more than $3\sigma$.
