Beta Functions
In quantum field theory, a beta function β(g) encodes the running of a coupling parameter, g. It is defined by the relation:
where μ is the energy scale of the given physical process. If the beta functions of a quantum field theory vanish, then the theory is scale-invariant.
The coupling parameters of a quantum field theory can flow even if the corresponding classical field theory is scale-invariant. In this case, the non-zero beta function tells us that the classical scale-invariance is anomalous.
Read more about this topic: Coupling Constant
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