Final answer:
Quantum Electrodynamics (QED) is a U(1) gauge theory that describes the interaction of electrons with photons. The theory has been successful in explaining and predicting electromagnetic phenomena at the quantum level.
Step-by-step explanation:
Quantum Electrodynamics (QED) is considered a U(1) gauge theory. In gauge theories, particles interact with each other through the exchange of gauge bosons. In the case of QED, the gauge boson is the photon. The U(1) refers to the symmetry group associated with the electromagnetic force. The theory describes the interaction of electrons (and other charged particles) with photons, and it has been extremely successful in explaining and predicting electromagnetic phenomena at the quantum level.