Tribrid inflation, type II leptogenesis, and observable gravitational waves in supersymmetric SU(3)_<i>c</i> × SU(2)_<i>L</i> × SU(2)_<i>R</i> × U(1)_<i>B-L</i>

Abstract We present a concrete realization of tribrid inflation within the framework of the gauge group SU(3) c × SU(2) L × SU(2) R × U(1) B-L . In this model, inflation is driven by the neutral components of SU(2) L triplet Higgs fields, which also play a central role in generating the observed baryon asymmetry of the universe via non-thermal leptogenesis. Tiny neutrino masses arise naturally through a type-II seesaw mechanism, facilitated by SU(2) R triplet Higgs fields. Supergravity corrections, stemming from the leading-order terms in a non-minimal Kähler potential, are essential in bringing the predictions of the scalar spectral index n s into agreement with the latest cosmological data, including the Atacama Cosmology Telescope Data Release 6, Planck 2018, and LB-BK18. A key feature of this model is the existence of a viable parameter space that predicts potentially observable primordial gravitational waves, with a tensor-to-scalar ratio r ≲ 0.001, placing it within reach of upcoming experiments.