Expectation values and vacuum currents of quantum fields

Understand

Theory of expectation values is presented as an alternative to S-matrix theory for quantum fields.

• This change of emphasis is conditioned by a transition from the accelerator physics to astrophysics and cosmology.
• The issues discussed are the time-loop formalism, the Schwinger - Keldysh diagrams, the effective action, the vacuum currents, and the effect of particle creation.