Gravitational Wave Gastronomy
  The symmetry breaking of grand unified gauge groups in the early Universe
often leaves behind relic topological defects such as cosmic strings, domain
walls, or monopoles. For some symmetry breaking chains, hybrid defects can form
where cosmic strings attach to domain walls or monopoles attach to strings. In
general, such hybrid defects are unstable, with one defect "eating" the other
via the conversion of its rest mass into the other's kinetic energy and
subsequently decaying via gravitational waves. In this work, we determine the
gravitational wave spectrum from 1) the destruction of a cosmic string network
by the nucleation of monopoles which cut up and "eat" the strings, 2) the
collapse and decay of a monopole-string network by strings that "eat" the
monopoles, 3) the destruction of a domain wall network by the nucleation of
string-bounded holes on the wall that expand and "eat" the wall, and 4) the
collapse and decay of a string-bounded wall network by walls that "eat" the
strings. We call the gravitational wave signals produced from the "eating" of
one topological defect by another gravitational wave gastronomy. We find that
the four gravitational wave gastronomy signals considered yield unique spectra
that can be used to narrow down the SO(10) symmetry breaking chain to the
Standard Model and the scales of symmetry breaking associated with the consumed
topological defects. Moreover, the systems we consider are unlikely to have a
residual monopole or domain wall problem.
