Cosmology of Theories BSM, Grand Unification, Early Universe Particle Physics, Phase Transitions in the Early Universe, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798

Abstract We present an SO(10) model in which a dimension five operator induces kinetic mixing at the GUT scale between the abelian subgroups U(1) B−L and U(1) R . We discuss in this framework gauge coupling unification and proton decay, as well as the appearance of superheavy quasistable strings with Gμ ~ 10−8 – 10−5, where μ denotes the dimensionless string tension parameter. We use Bayesian analysis to show that for Gμ values ~ 4 × 10−7 − 10−5, the gravitational wave spectrum emitted from the quasistable strings is in good agreement with the recent pulsar timing array data. Corresponding to Gμ values ~ 10−8 − 2 × 10−7, proton decay is expected to occur at a rate accessible in the Hyper-Kamiokande experiment. Finally, we present the gravitational wave spectrum emitted by effectively stable strings with Gμ ≈ 10−8 that have experienced a certain amount of inflation. This can be tested with future detectors in the μHz frequency range.