Baryogenesis from `electrogenesis' in a scalar field dominated epoch

Scalar fields can play a dominant role in the dynamics of the Universe untilshortly before nucleosynthesis. Examples are provided by domination by akinetic mode of a scalar field, which may be both the inflaton and the latetime `quintessence', and also by more conventional models of reheating. Theresultant modification to the pre-nucleosynthesis expansion rate can allowsolely an asymmetry in right handed electrons to produce a net baryon asymmetrywhen reprocessed by the anomalous B+L violating processes of the standardmodel. The production of such a source asymmetry - what we term`electrogenesis' - requires no additional B or L violation beyond that in thestandard model. We consider a specific model for its generation, by a simpleperturbative out of equilibrium decay of Higgs like scalar fields withCP-violating Yukawa couplings to the standard model leptons. We show that,because of the much enhanced expansion rate, such a mechanism can easilyproduce an adequate asymmetry from scalars with masses as low as 1 TeV. Kineticmode domination is strongly favoured because it evades large entropy releasewhich dilutes the asymmetry. We also discuss briefly the effect of the abelianhypercharge anomaly.Comment: 25 pages, 2 figure