The earth vibrates with analogies: The Dirac sea and the geology of the vacuum

Yoichiro Nambu and the Concept of Apparent Vacuum: A Stepping Stone to Spontaneous Symmetry Breaking

“…As a comprehensive historical analysis reveals, this affordance arose, at least partly, from the concurrence of a few heterogenous elements: Nambu's education in Tokyo, which had induced in him an interest in solid‐state physics, [ 12 ] and the different course that Dirac's picture took among some Japanese physicists, a course influenced by their tendency to produce concrete representations of the abstract objects as well as the “substantialistic” philosophy promoted by the Yukawa‐Sakata school (see refs. [2] and [13]). In light of these elements, one should then read the otherwise enigmatic remark that Nambu would make many years later on how “under the influence of the Yukawa‐Sakata school” he had always regarded “Dirac's assumption of the filling of the negative energy states in the vacuum” not as “a mathematical trick but a reality.” [ 14 ] The story here reveals the sense of these words.…”