Gravitational Waves from Quasi-stable Strings

Understand

We estimate the stochastic gravitational wave spectrum emitted from a network of cosmic strings in which the latter are effectively stable against breaking by monopole pair creation.

• The monopoles are produced at a higher scale from an earlier symmetry breaking and experience significant inflation before reentering the horizon.
• This gives rise to monopole-antimonopole pairs connected by string segments and the string loop formation essentially ceases.
• As a consequence, the lower frequency portion of the gravitational wave spectrum is suppressed relative to the no-inflation case with stable strings, which evades the stringent PPTA bound on the dimensionless string tension $G\mu$.