Quantum fields with classical interactions

Understand

We describe basic types of free fields (1) neutral scalar bosons; (2) massive vector bosons; (3) massless vector bosons; (4) charged scalar bosons; (5) Dirac fermions; (6) Majorana fermions.

• We also consider free field perturbed by a linear or quadratic perturbation involving a classical (c-number) function: (1) neutral scalar bosons interacting with a linear source; (2) neutral scalar bosons interacting with a mass-like perturbation; (3) massive photons interacting with an classical current; (4) massless photons interacting with an classical current.
• (5) charged scalar bosons interacting with an electromagnetic potential; (6) Dirac fermions interacting with an electromagnetic potential.