Baryogenesis via gravitational spontaneous symmetry breaking

We study baryogenesis in effective field theories where a $\mathrm{U}(1{)}_{B-L}$-charged scalar couples to gravity via curvature invariants. We analyze the general possibilities in such models, noting the relationships between some of them and existing models, such as Affleck-Dine baryogenesis. We then identify a novel mechanism in which $\mathrm{U}(1{)}_{B-L}$ can be broken by couplings to the Gauss-Bonnet invariant during inflation and reheating. Using analytic methods, we demonstrate that this mechanism provides a new way to dynamically generate the net matter-antimatter asymmetry observed today and verify this numerically.

Figure 1

The equation of state as a function of time that gives rise to the parameterization of the Hubble constant given in Eq. (35).

Figure 2

Left: The evolution of $|\varphi {|}_{\min }(t)$ calculated analytically [using the parameterization in Eq. (35)] and the results of the numerical integration for $|\varphi |(t)$. Right: The evolution of real and imaginary parts of the scalar.

Figure 3

The ratio $n_{B-L}/s$ as a function of time.