Standard Model extension with gravity and gravitational baryogenesis

The Standard Model extension with the inclusion of gravity is studied in the framework of the gravitational baryogenesis, a mechanism to generate the baryon asymmetry based on the coupling between the Ricci scalar curvature and the baryon current (∂μR)Jμ. We show that, during the radiation era of the expanding universe, a non-vanishing time derivative of the Ricci curvature arises as a consequence of the coupling between the coefficients for the Lorentz and CPT violation and Ricci's tensor. The order of magnitude for these coefficients are derived from current bounds on baryon asymmetry.