Conformally-flat gravitational analogues to the Schwinger effect

We study particle creation for scalar fields in conformally flat spacetimes using resummed heat-kernel techniques. We make use of an analogy between quantum scalar fields in conformally flat spacetimes and scalar field theories with a Yukawa coupling in Minkowski space. The correspondence holds exactly at the level of the effective action and includes nonconformal curvature couplings. This framework provides access to particle creation at strong curvature. In a radiation dominated universe, the particle production rates in arbitrary dimensions are independently confirmed through explicit calculations of the Bogoliubov coefficients. We also find new exact gravitational analogues of the Schwinger effect in quantum field theory in curved spacetime.