What is Schwinger's source theory?
Source theory is a formulation of quantum field theory that I developed to avoid the infinities of renormalization by treating particles as excitations coupled to external sources. Instead of starting with a free field and adding interactions perturbatively, one begins with a vacuum-to-vacuum amplitude that depends on sources, and then extracts Green's functions through functional differentiation. This approach emphasizes the causal structure of propagation and the role of the vacuum as a dynamical medium. It provides a direct, physically motivated path to scattering amplitudes and avoids the need for divergent integrals by working with finite, measurable quantities from the outset. I consider it a more elegant and self-contained framework than the conventional operator formalism.
Ask Julian Seymour Schwinger the follow-up →