Julian Schwinger (February 12, 1918 – July 16, 1994) is best known for his work on the theory of quantum electrodynamics (QED), in particular for developing a relativistically invariant perturbation theory, and for renormalizing QED to one loop order. For his substantial contributions to many areas, he is widely recognized as one of the greatest physicists of the twentieth century. Along with Feynman and Tomonaga, he won the 1965 Nobel Prize in Physics for his work on quantum electrodynamics.
Starting as a leader in nuclear physics, the discoverer of tensor forces, Schwinger pioneered powerful variational methods in classical electrodynamics and was the American developer of the theory of synchrotron radiation. He is responsible for much of modern quantum field theory, including a quantum version of the action principle, and the equations for the Green’s functions that define the content of such theories. He laid the foundations for non-equilibrium quantum statistical mechanics and for quantum gravity. He developed the first electroweak model, an SU(2) gauge group spontaneously broken to electromagnetic U(1) at long distances. He also explored the first example of confinement in the Schwinger model, quantum electrodynamics in 1 + 1 dimensions. He was responsible for the theory of multiple neutrinos, Schwinger terms, the theory of the spin-3/2 field, and discovered anomalies in quantized fields. He advanced the theory of magnetic charge, monopoles and dyons. As Schwinger contributed to many more areas in classical and quantum physics, the above is just selection of topics.