Probing the scale of grand unification with gravitational waves

Physics letters / B B809, 1-5 (2020). doi:10.1016/j.physletb.2020.135764
The spontaneous breaking of U(1)$_{B−L}$ around the scale of grand unification can simultaneously account for hybrid inflation, leptogenesis, and neutralino dark matter, thus resolving three major puzzles of particle physics and cosmology in a single predictive framework. The $B−L$ phase transition also results in a network of cosmic strings. If strong and electroweak interactions are unified in an SO(10) gauge group, containing U(1)$_{B−L}$ as a subgroup, these strings are metastable. In this case, they produce a stochastic background of gravitational waves that evades current pulsar timing bounds, but features a flat spectrum with amplitude h$^2$Ω$_{GW}$∼10$^{−8}$ at interferometer frequencies. Ongoing and future LIGO observations will hence probe the scale of $B−L$ breaking.
Published by North-Holland Publ., Amsterdam