Nonlinear Abelian gauge fixing
= Nonlinear Abelian gauge fixing
For an <Abelian gauge theory> with $A_\mu\mapsto A_\mu+\partial_\mu\alpha$, a nonlinear gauge functional $F[A]$ has <Faddeev-Popov determinant> $\det(\delta F[A+\partial\alpha]/\delta\alpha)$. This operator can depend on $A$ even though the <Adjoint representation> of $U(1)$ is trivial. Consequently <Faddeev-Popov ghost fields> need not decouple in a nonlinear Abelian gauge, unlike a field-independent linear gauge condition.