出典:Wikipedia
出典:『Wikipedia』 (2011/07/22 17:11 UTC 版)
In quantum field theory the vacuum expectation value (also called condensate or simply VEV) of an operator is its average, expected value in the vacuum. The vacuum expectation value of an operator O is usually denoted by
. One of the best known examples of an observable physical effect that results from the vacuum expectation value of an operator is the Casimir effect.