Vacuum expectation value |Quantum field theory| 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. - The Higgs field has a
vacuum expectation value of 246 GeV (Amsler, C.; Doser, M.;
Antonelli, M.; Asner, D.; Babu, K.; Baer, H.; Band, H.; Barnett,
R. et al. (2008). "Review of Particle Physics⁎". Physics Letters
B 667: 1. doi:10.1016/j.physletb.2008.07.018. ) This nonzero
value underlies the Higgs mechanism of the Standard Model. - The
chiral condensate in Quantum chromodynamics, about a factor of a
thousand smaller than the above, gives a large effective mass to
quarks, and distinguishes between phases of quark matter. This
underlies the bulk of the mass of most hadrons. - The gluon
condensate