Gravitational Baryogenesis at the Bounce, Where the Ricci Scalar Changes Fastest

Gravitational baryogenesis couples the derivative of the Ricci scalar to the baryon current, so that a changing spacetime curvature acts as a chemical potential for baryon number. The coupling is negligible in a slowly evolving universe and largest where curvature changes fastest: at a bounce. This paper computes the effect with the curvature scale set by the torsion density ceiling. The maximum expansion rate is H_max = 2.33e+24 per second, or 1.53e+00 GeV, giving a curvature-derivative scale Rdot of 3.61e+00 GeV^3. With the coupling suppressed by a scale M_star equal to the Planck mass, the yield at decoupling temperature 1e12 GeV is only 8.64e-53; matching the observed yield at that temperature requires M_star near 1.22e-02 GeV. The mechanism is therefore viable at a bounce only with a suppression scale well below the Planck mass, a requirement that any concrete model must justify. Computed from stated assumptions, not measured.