NEW APPROACH. “A chemical potential can be assigned for the boundary–interaction region, responsible for keeping baryons and antibaryons separated, as a function of the antimatter density. A baryon/antibaryon-symmetrical Universe with large domains is demonstrated not to be compatible with a γ-ray background; the difference in the amount of antimatter can therefore be ascribed to a possible contribution to the definition of the chemical potential.”
https://www.mdpi.com/2218-1997/7/9/347/htm