The evolution of an axionic field after inflation offers an explanation for the matter-antimatter asymmetry of the universe. During inflation, light scalar fields, including axions expected to arise from string theory and in various field-theoretic models, develop large expectation values. These fields relax to the minima of their effective potentials during or after reheating. An oscillating axion coupled to the electroweak gauge fields generates an effective chemical potential for the fermion number, which, in the presence of lepton number-violating processes, generates a lepton asymmetry that is partly converted to a baryon asymmetry by sphalerons. The observed matter-antimatter asymmetry can be explained in a broad range of parameter values with the reheating temperatures being at least of order 10^12 GeV, and for all right-handed neutrino masses close to the scale of grand unification. Our mechanism is hence complementary to thermal leptogenesis with respect to the range of allowed parameter values.
A. Kusenko, K. Schmitz and T. Yanagida
Mon, 8 Dec 14
Comments: 5 pages, 2 figures