Stochastic gravitational-wave background from metastable cosmic strings

Jul 9, 2021
31 pages
Published in:
  • JCAP 12 (2021) 12, 006
  • Published: Dec 3, 2021
e-Print:
Report number:
  • CERN-TH-2021-107,
  • DESY 21-101

Citations per year

202120222023202420251018322
Abstract: (IOP)
A metastable cosmic-string network is a generic consequence of many grand unified theories (GUTs) when combined with cosmic inflation. Metastable cosmic strings are not topologically stable, but decay on cosmic time scales due to pair production of GUT monopoles. This leads to a network consisting of metastable long strings on superhorizon scales as well as of string loops and segments on subhorizon scales. We compute for the first time the complete stochastic gravitational-wave background (SGWB) arising from all these network constituents, including several technical improvements to both the derivation of the loop and segment contributions. We find that the gravitational waves emitted by string loops provide the main contribution to the gravitational-wave spectrum in the relevant parameter space. The resulting spectrum is consistent with the tentative signal observed by the NANOGrav and Parkes pulsar timing collaborations for a string tension of Gμ_{μ} ∼ 10117^{-11…-7} and has ample discovery space for ground- and space-based detectors. For GUT-scale string tensions, Gμ_{μ} ∼ 1087^{-8…-7}, metastable strings predict a SGWB in the LIGO-Virgo-KAGRA band that could be discovered in the near future.
Note:
  • 31 pages, 6 figures. v2: signal recently reported by the Parkes Pulsar Timing Array (PPTA) collaboration [2107.12112] added to Figs. 2 to 4
  • Cosmic strings
  • domain walls
  • monopoles
  • primordial gravitational waves (theory)
  • particle physics - cosmology connection
  • gravitational waves / experiments
  • gravitational radiation: stochastic
  • cosmic string: network
  • gravitational radiation: spectrum
  • grand unified theory