The Schwinger effect, also known as vacuum pair production, is a phenomenon predicted by quantum field theory in the presence of a strong electric field. It describes the spontaneous creation of particle-antiparticle pairs from the vacuum due to the intense electromagnetic field.
The concept was first formulated by the physicist Julian Schwinger in 1951. According to the theory, when an electric field becomes sufficiently strong, it can exert enough energy to create particle-antiparticle pairs (such as electrons and positrons) out of the vacuum. In the absence of an electric field, the vacuum is typically considered to be devoid of particles. However, the strong electric field can cause the vacuum to "boil" with particle-antiparticle pairs spontaneously emerging and annihilating each other.
The Schwinger effect arises from the nonlinearity of quantum electrodynamics (QED), the quantum field theory describing the electromagnetic interaction. The strong electric field distorts the vacuum, leading to the production of real particles that can be detected experimentally.
The probability of vacuum pair production depends on the strength of the electric field. When the field exceeds a critical value, called the Schwinger critical field, the rate of pair production becomes significant. The critical field is extremely high, on the order of 10^18 volts per meter, which makes it difficult to directly observe the effect in laboratory settings.
The Schwinger effect is a significant prediction of quantum field theory, demonstrating the nontrivial behavior of the vacuum in the presence of strong fields. It has implications in various areas of physics, including cosmology, where it is believed to play a role in the early universe during inflation or in the vicinity of black holes, where strong electric fields can be present.