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Vacuum Expectation Value




This concept is important for working with Correlation Functions in Quantum Field Theory . It is also important in Spontaneous Symmetry Breaking . Examples are:

The observed Lorentz Invariance of space-time allows only the formation of condensates which are Lorentz Scalars and have vanishing Charge . Thus Fermion condensates must be of the form \langle\overline\psi\psi angle, where ψ is the fermion field. Similarly a tensor field, Gμν, can only have a scalar expectation value such as \langle G_{\mu
u}G^{\mu
u} angle.

In some Vacua of String Theory , however, non-scalar condensates are found. If these describe our Universe , then Lorentz Symmetry Violation may be observable.


SEE ALSO