Higher loop corrections to the current of created pairs in the lengthy electric pulse

The Schwinger current, arising from vacuum breakdown in the presence of a strong constant electric pulse background, is well known and has been calculated in numerous studies. It originates from the amplification of zero-point fluctuations. However, we find that higher-loop corrections involve hidden redistributions of the level populations of charged particles and photons. These redistributions lead to corrections to the current, which become significant for sufficiently long pulses and ultimately modify Schwinger’s expression for the current.