Baryogenesis in a flat direction with neither baryon nor lepton charge

We present a new scenario of baryogenesis in a flat direction with neither baryon nor lepton charge. By imposing the Peccei-Quinn (PQ) symmetry on the standard particles, the phase of the flat direction derivatively couples to the linear combination of the PQ and $B-L$ currents. The non-zero expectation value of the flat direction and the existence of A-terms naturally lead to CPT violation. The distinctive feature of our scenario is that the CPT violation of the PQ sector is transmitted to the $B-L$ sector if there exists an interaction violating the PQ and $B-L$ symmetries simultaneously and it is in thermal equilibrium. Thus, the $B-L$ asymmetry, which is converted to the baryon asymmetry through the sphaleron effects, is generated from `nothing' {\it i.e.,} a flat direction which has neither baryon nor lepton charge.