Yoichiro Nambu later applied it to all production and annihilation of particle-antiparticle pairs, stating that "the eventual creation and annihilation of pairs that may occur now and then, is no creation nor annihilation, but only a change of directions of moving particles, from past to future, or from future to past."
Yoichiro Nambu later applied his theory to all production and annihilation of particle-antiparticle pairs, stating that "the creation and annihilation of these pairs are not actual creations or annihilations but merely a change in the direction of moving particles, shifting them from the past to the future or vice versa."