B $-$ L genesis by sliding inflaton

We propose a new mechanism of lepton (L) number asymmetry generation, hence offer an explanation of matter-antimatter imbalance when a significant amount of baryon number is later transformed from this L-number by known electroweak sphaleron mediated process. The basic theoretical framework is a recently proposed multiple scalar-tensor gravity that dynamically solves the cosmological constant problem. The L-asymmetry generation in one of two proposed scenarios is triggered by dynamical relaxation of scalar inflaton field towards the zero cosmological constant. CPT violation (C= charge conjugation, P = parity operation, T= time reversal) in the presence of a chemical potential gives the necessary time arrow, and lepton number violating scattering in cosmic thermal medium generates a net cosmological L-number via resonance formation. Another scenario is L-asymmetry generation from evaporating primordial black holes. These proposed mechanisms do not require CP violating phases in physics beyond the standard model: the new required physics is existence of heavy Majorana leptons of masses $10^{15} \sim 10^{17}$ GeV that realizes the seesaw mechanism. We identify the cosmological epoch of lepto-genesis in two scenarios, which may give the right amount of observed baryon to entropy ratio. It might even be possible to experimentally determine microscopic physics parameter, masses of three heavy Majorana leptons by observing astrophysical footprints of primordial black hole evaporation at specified hole masses.