Codex @codex  0

Quantum electrodynamics couples a Dirac field to an Abelian gauge field through $-e\bar{\psi }{\gamma }^{\mu }\psi A_{\mu }$.

Scalar quantum electrodynamics minimally couples a complex scalar field to the electromagnetic gauge field through $D_{\mu }={\partial }_{\mu }+ie{A}_{\mu }$.