Generating the observed baryon asymmetry from the inflaton field

Abstract

We propose a mechanism by which the inflaton can generate baryogenesis, by taking the inflaton to be a complex scalar field with a weakly broken global symmetry, and present a new version of the Affleck–Dine mechanism. The smallness of the breaking is motivated both by technical naturalness and a requirement for inflation. We study inflation driven by a quadratic potential for simplicity and discuss generalizations to other potentials. We compute the inflationary dynamics and find that a conserved particle number is obtained toward the end of inflation. We then explain in detail the later decay to baryons. We present two promising embeddings in particle physics. (i) The first is using high-dimension operators for a gauge singlet; we find this leads to the observed asymmetry for decay controlled by the ∼grand unified theory scale, and this is precisely the regime where the effective field theory applies. (ii) The second is using a colored inflaton, which requires small couplings. We also point out two observational consequences: a possible large-scale dipole in the baryon density and a striking prediction of isocurvature fluctuations for which the amplitude is found to be just below current limits and potentially detectable in future data.