U(1) gauge symmetry
= U(1) gauge symmetry
{c}
For $D_\mu=\partial_\mu+ieA_\mu$, the local U(1) transformation is
$$
\psi\mapsto e^{ie\chi}\psi,
\qquad
A_\mu\mapsto A_\mu-\partial_\mu\chi.
$$
= U(1) gauge symmetry
{c}
For $D_\mu=\partial_\mu+ieA_\mu$, the local U(1) transformation is
$$
\psi\mapsto e^{ie\chi}\psi,
\qquad
A_\mu\mapsto A_\mu-\partial_\mu\chi.
$$