  The nature of dark matter remains one of the greatest unsolved mysteries in
elementary particle physics. It might well be that the dark matter particle
belongs to a dark sector completely secluded or extremely weakly coupled to the
visible sector. We demonstrate that gravitational waves arising from first
order phase transitions in the early Universe can be used to look for
signatures of such dark sector models connected to neutron physics. This
introduces a new connection between gravitational wave physics and nuclear
physics experiments. Focusing on two particular extensions of the Standard
Model with dark U(1) and SU(2) gauge groups constructed to address the neutron
lifetime puzzle, we show how those signatures can be searched for in future
gravitational wave and astrometry experiments.
