Pair production in a strong slowly varying magnetic field: the effect of a background gravitational field

The production probability of an $e^{-}-e^{+}$ pair in the presence of a strong, uniform and slowly varying magnetic field is calculated by taking into account the presence of a background gravitational field. The curvature of the spacetime metric induced by the gravitational field not only changes the transition probabilities calculated in the Minkowski spacetime but also primes transitions that are strictly forbidden in absence of the gravitational field.