GUT's have the guts to defy sphalerons

Abstract

We show that the baryon asymmetry produced by the out of equilibrium decay of heavy GUT scalars can be the baryon asymmetry that is observed today. No restrictions need be imposed on the initial values of B, L and B − L, nor on the neutrino masses; no new symmetries need be gauged nor new fermions introduced. We find two mechanisms that can bring this about for any GUT gauge group. Two illustrative models are discussed that are robust, and need just two (at most four) more GUT scalar fields than the minimal model. The additional scalar fields can also help in generating an adequately large value of the CP violation parameter and in efficiently annihilating the monopoles. Our work should firmly re-establish heavy GUT scalars as probable progenitors of today's baryon asymmetry.