Description
Grand unified theory (GUT) provides a rationale for the arbitrariness of the Standard Model (SM) and explains many enigmas of nature at the outset of a single gauge group. We will discuss the realizations of 'metastable' strings (MSS), 'quasistable' strings (QSS), and 'walls bounded by strings' (WBS) in SO(10) GUTs. We will explore the stochastic gravitational wave background emitted from such networks of composite structures. We will discuss the gravitational waves emitted from MSS, QSS, and WBS with superheavy (~GUT scale) strings, which can explain the recent exciting evidence of stochastic gravitational waves in NANOGrav and other pulsar timing array data.
