Center for Theoretical Physics of the Universe (CTPU-PTC)

Metastable strings from supersymmetric $U(1)_{B-L}$ flat direction and NANOGrav 15 year data

by Rinku Maji (Jeonbuk National U.)

Seminar Room (CTPU)

Seminar Room


We discuss the formation of monopoles connected by strings in D-flat breaking of $U(1)_{B?L}$ extensions of the minimal supersymmetric standard model. The gravitational from these 'metastable' composite structures can be responsible for the signal of a stochastic gravitational wave background (GWB) recently reported by NANOGrav collaborations around the nanoHertz frequencies. A phase of thermal inflation arises due to the flatness of the direction, and the reheating temperature is relatively low. Therefore, the GWB spectrum is suppressed at frequencies higher than the characteristic frequency set by the reheating temperature and naturally satisfies the bound from the third run advanced LIGO-VIRGO data around the decaHertz frequencies. Notably, forthcoming spaced-based experiments such as LISA can probe the cutoff frequency, providing an indirect clue of the soft SUSY-breaking mass parameter scale.