We calculate the baryon asymmetry created by the decay of a pseudo Nambu-Goldstone boson (PNGB) whose interactions violate baryon number conservation. Our results are in disagreement with previous results in the original spontaneous baryogenesis models for the asymmetry produced by the decay of an oscillating scalar field with $B$-number-violating derivative couplings; we find that the net baryon number density is proportional to ${\theta }_i^3,$ where ${\theta }_i$ is the amplitude of the PNGB field in natural inflation at the onset of reheating. While our calculation of the asymmetry is carried out in the context of natural inflation our approach is generally valid for baryogenesis models using decaying classical fields. We include a complete derivation of the number density of particles produced by the decay of a classical scalar field.

• Received 18 April 1997

DOI:https://doi.org/10.1103/PhysRevD.56.6155