Title: Complementary probes of weakly-coupled and high-scale BSM:
        CMB, Gravitational Waves and Laboratory tests for Leptogenesis and Dark Matter
Leptogenesis usually involves high scales and it is hard to test in laboratories, Here we will discuss probing high scale and intermediate scale leptogenesis via primordial sources of Gravitational Waves from inflationary tensor perturbations, thermal phase transitions and domain walls. First  we will show leptogenesis in B−L symmetry breaking scenario  associated with a strong first-order phase transition that gives rise to detectable gravitational waves (GWs) via bubble collision. And the possible future GW experiments can effectively probe leptogenesis over a wide range of the B−L symmetry-breaking scale. Second we propose a novel way of probing high-scale Dirac leptogenesis, a viable alternative to the canonical leptogenesis scenario where the total lepton number is conserved, keeping light standard model neutrinos purely Dirac. This leads to GW signals from collapsing domain walls. We find that most of the near-future GW observatories will be able to probe Dirac leptogenesis scales all the way up to 10ˆ11 GeV. Third we will show how inflationary tensor perturbations and its detectability may shed light upon high-scale leptogenesis and dark matter. Last we will show complementary tests for freeze-in DM via GW and long-lived particle searches.  In particular, we show that freeze-in scenarios can be searched by various experiments such as DUNE, FASER, FASER-II, MATHUSLA, SHiP, etc. complementary observables for GW detectors such as LISA and u-DECIGO.