A predicted physical phenomenon whereby matter is created by a strong electric field: electron–positron pairs spontaneously appear, causing the field to decay.
A prediction of quantum electrodynamics, also called the Sauter–Schwinger effect, the Schwinger mechanism, or Schwinger pair production.
It has never been observed: pair production is exponentially slow below the Schwinger limit of roughly 10^18 V/m, unreachably strong for current laser facilities.