Yoichiro Nambu

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

"The idea of spontaneous symmetry breaking was introduced into particle physics by Nambu ... in 1960. He suggested that the low mass and low-energy interactions of s could be understood as a reflection of a spontaneously-broken chiral symmetry, would have been exact if the up and down quarks were massless. His suggestion was that light quarks condense in the vacuum, much like the s of superconductivity. When this happens, the ‘hidden’ chiral symmetry causes the pions’ masses to vanish, and fixes their low-energy s to s, s and each other."

"Yoichiro Nambu was one of the most influential theoretical physicists of the twentieth century. His deep and unexpected insights often took years for others to understand and fully appreciate. They include: spontaneous symmetry breaking, for which he was awarded half of the 2008 Nobel Prize in Physics; the theory of quarks and gluons; and string theory."

"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 Bogolyubovs."