Gravitational waves from first order phase transitions as a probe of an
  early matter domination era and its inverse problem
  We investigate the gravitational wave background from a first order phase
transition in a matter-dominated universe, and show that it has a unique
feature from which important information about the properties of the phase
transition and thermal history of the universe can be easily extracted. Also,
we discuss the inverse problem of such a gravitational wave background in view
of the degeneracy among macroscopic parameters governing the signal.
