Gravitational waves and monopoles dark matter from first-order phase
  transition
  We study the possibility of monopoles serving as dark matter when they are
produced during the first-order phase transition in the dark sector. Our study
shows that dark monopoles can contribute only a small piece of dark matter
relic density within parameter spaces where strong gravitational waves can be
probed by ET and CE, and the monopoles can contribute a sizable component of
the observed dark matter relic density for fast phase transitions with short
duration.
