structural:expansion, information:filtering, structural:scholar_edition
Pure gauge

A pure gauge is the set of field configurations obtained by a gauge transformation on the null-field configuration, i.e., a gauge transform of zero. So it is a particular "gauge orbit" in the field configuration's space.

Thus, in the abelian case, where A μ (x) → A μ ′ (x) = A μ (x) + ∂ μ f (x) {\displaystyle A_{\mu }(x)\rightarrow A'_{\mu }(x)=A_{\mu }(x)+\partial _{\mu }f(x)}, the pure gauge is just the set of field configurations A μ ′ (x) = ∂ μ f (x) {\displaystyle A'_{\mu }(x)=\partial _{\mu }f(x)} for all f (x).