We propose a new alternative for baryogenesis which resolves a number of the problems associated with grand unified theory (GUT) and electroweak scenarios, and which may allow baryogenesis even in modest extensions of the standard model. If the Universe never reheats above the electroweak scale following inflation, GUT baryon production does not occur, and at the same time thermal sphalerons, gravitinos, and monopoles are not produced in abundance. Nevertheless, nonthermal production of sphaleron configurations via preheating could generate the observed baryon asymmetry of the Universe.

• Received 22 February 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.1502