We apply the in-out formalism, a nonperturbative method, to QED in a dS spacetime, and investigate the effect of a uniform magnetic field background on scalar QED pair production. The results describe how the cosmic magnetic field affects the pair production rate in cosmological setups. In the case of a strong electromagnetic background the current responds as E⋅B, while in the infrared regime, it responds as B/E, which leads to a phenomenon of infrared hyperconductivity. The origin of magnetogenesis may be explained by Schwinger mechanism.
The one-loop effective action (vacuum polarization) in parallel uniform electric and magnetic fields in the (A)dS spacetime is obtained via the gamma-function regularization, which is consistent with the vacuum persistence and thereby the Schwinger effect. The effect of curvature on the QED vacuum polarization is explored in the context of astrophysics, black holes, and cosmology.