Clergyman's

It was the great multiplicity of the hadrons that led to the formulation of the quark model. Without some organizing principle such a large collecton of particles seemed unwieldy, and the possibility that they might all be elementary offended those who hold the conviction, or at leas the fond wish, that nature should be simple.
- Yoichiro Nambu

Ideas and techniques known in quantum electrodynamics have been applied to the Bardeen-Cooper-Schrieffer theory of superconductivity. In an approximation which corresponds to a generalization of the Hartree-Fock fields, one can write down an integral equation defining the self-energy of an electron in an electron gas with phonon and Coulomb interaction. The form of the equation implies the existence of a particular solution which does not follow from perturbation theory, and which leads to the energy gap equation and the quasi-particle picture analogous to Bogolyubov's.
- Yoichiro Nambu