  The baryon asymmetry of the Universe is one of the central motivations to
expect physics beyond the Standard Model. In this Snowmass white paper, we
review the challenges and opportunities in testing some of the central
paradigms that predict physics at scales low enough to expect new experimental
data in the next decade. Focusing on theoretical ideas and some of their
experimental implications, in particular, we discuss neutron-antineutron
transformations, flavor observables, next generation colliders, future neutron
facilities, gravitational waves, searches for permanent electric dipole
moments, $0\nu \beta \beta $ decay and some future large underground
experiments as methods to test post-sphaleron baryogenesis, electroweak
baryogenesis, mesogenesis and low scale leptogenesis. Finally, we comment on
the cases where high scale physics can be probed through some of these same
mechanisms.
