CAS, Shanghai Astron Observ, Shanghai 200030, Peoples R China
; Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China
; CAS, Natl Astron Observ, Beijing 100012, Peoples R China
; CAS, Inst High Energy Phys, Beijing 100049, Peoples R China
; CAS, Inst Theoret Phys, Beijing 100080, Peoples R China
; Hangzhou Teachers Coll, Hangzhou 310018, Peoples R China
The role of the auxiliary scalar field phi of BD theory in baryon number asymmetry is discussed in this paper. We consider a derivative coupling of this gravitational scalar field to the baryon current J(B)(mu) or the current of the baryon number minus lepton number J(B-L)(mu), based on a series of works of R. Morganstern about the Brans-Dicke cosmology. We find that the spontaneous baryogenesis by this coupling is able to yield sufficient baryon asymmetry n(B)/s similar to 10(-10) provided the time of the grand unification is a little bit earlier. In addition, Davoudiasl et al have recently introduced a new type of interaction between the Ricci scalar R and the bayon current J(mu), partial derivative(mu), RJ(mu) and also proposed a mechanism for baryogenesis, the gravitational baryogenesis. However, the Einstein equation tells us that (R) over circle = 0 in the radiation-dominated epoch of the standard FRW cosmology. In this paper we reconsider the feasibility of having gravitational baryongenesis with such a form of interaction in radiation-filled BD cosmology. We show that (R) over circle does not vanish in this case and the required baryon number asymmetry can also be achieved.