Gravitational Wave Signals from Multiple Hidden Sectors
  We explore the possibility of detecting gravitational waves generated by
first order phase transitions in multiple dark sectors. Nnaturalness is taken
as a sample model that features multiple additional sectors, many of which
undergo phase transitions that produce gravitational waves. We examine the
cosmological history of this framework and determine the gravitational wave
profiles generated. These profiles are checked against projections of
next-generation gravitational wave experiments, demonstrating that multiple
hidden sectors can indeed produce unique gravitational wave signatures that
will be probed by these future experiments.
