LINEAR-RESPONSE THEORY APPROACH TO SPONTANEOUS BARYOGENESIS

We reconsidered the spontaneous baryogenesis mechanism by Cohen, Kapla n and Nelson. Using linear response theory, we calculate the modificat ions on the thermal averages of the charges of the system due to the p resence of a space time dependent ''charge potential'' for a quantum n umber not orthogonal to baryon number. The local equilibrium configura tion is discussed, showing that, as a consequence of non zero densitie s for conserved charges, the B + L density is driven to non zero value s by sphaleronic processes. Solving a rate equation for the baryon num ber generation, we obtain an expression for the final baryon asymmetry of the Universe containing the relevant parameters of the bubble wall , i.e. its velocity, its width, and the width of the region in which s phalerons are active. Compared to previous estimates in which transpor t effects were not taken into account, we find an enhancement of nearl y three orders of magnitude in the baryon asymmetry. Finally, the role of QCD sphalerons in cooperation with transport effects is analyzed, showing that the net result depends crucially on the particle species which enter into the charge potential.