Julian Seymour Schwinger was an American theoretical physicist. He shared the 1965 Nobel Prize in Physics with Richard Feynman and Shin'ichirō Tomonaga "for their fundamental work in quantum electrodynamics (QED), with deep-ploughing consequences for the physics of elementary particles". He developed a relativistically invariant perturbation theory, and renormalized QED to one loop order. Schwinger was a physics professor at several universities.