Thursday, December 06, 2012

Classifications of Theoretical Physicists, Especially of Yukawa and Tomonaga

The theoretical physicist Susumu Kamefuchi published an essay entitled "Gramsci's words, Yukawa, Tomonaga, and Sakata" [1]. At the beginning of the essay, Kamefuchi quotes the following words:
Passage from knowing to understanding and to feeling and vice versa from feeling to understanding and to knowing —Antonio Gramsci, "Prison Notebooks" [2]

Kamefuchi likens the three elements in the above quotes, i.e., feeling, understanding and knowing to three stages of research in theoretical physics, i.e., (I) practitioner's stage, (II) theorist's stage and (III) natural philosopher's stage. Then, he thinks about the question in which stage each of Hideki Yukawa, Sin-Itiro Tomonaga, and Shoichi Sakata was good at working or liked to work, in order to classify them into corresponding three types, I, II and III, of physicists.

Sakata was called a person of methods and his successful studies, i.e., the two-meson theory and the Sakata model of elementary particles were phenomenological. From these facts, Kamefuchi classifies Sakata into type I.

Tomonaga had an excellent mastery of mathematics and expertise in constructing theories based on different physical requirements, producing the super‐many‐time theory, which lead him to the finding of the renormalization method and to the winning of Nobel Prize. Thus, Kamefuchi classifies him into type II.

Yukawa's work to create a comprehensive theory of particles starting from "nonlocal fields" or "elementary domains" corresponded to the process of going from knowing to understanding and to feeling, but was not completed. However, Yukawa said in his later year, "Such a fundamental theory was my ultimate purpose, and the meson theory was a byproduct on my way." Yukawa often presented his opinion about various cultural problems (creativity, genius, learning, peace, etc.), displaying his characteristic of being an excellent thinker in culture as well as in physics. From these facts, Kamefuchi classifies Yukawa into type III.

Kamefuchi's essay concludes as follows:
The fact that Yukawa, Tomonaga and Sakata belonged to the three different types was rather lucky to the development of particle theory in Japan. The three leaders played the role of antithesis against each other so that the study of particle physics in our country made a balanced progress. […] I believe that this was the basis of the Nobel-prize winning studies by the physicists of the next generation, Yoichiro Nambu, Masatoshi Koshiba, Toshihide Maskawa and Makoto Kobayashi.

Kamefuchi's classification scheme of physicists reminds me of a similar classification proposed by Yoichiro Nambu. His classification as summarized by himself is as follows [3]:
Once I classified theoretical physicists into three types according to their different styles of approach, and called them Heisenberg (H), Einstein (E) and Dirac (D) modes, referring to their most characteristic contributions respectively, i.e., quantum mechanics, theory of gravitation and the Dirac equation. Heisenberg’s is heuristic, bottom-up and inductive. Einstein’s is axiomatic, top-down and deductive. Dirac’s is abstract, revolutionary and esthetic.

As for the modes to which Yukawa and Tomonaga belongs, Nambu writes as follows [3]:
It would be safe to say that Yukawa belonged to H when he proposed the meson. He failed in E when he tried his hand at nonlocal theory. I have a bit of difficulty applying this to Tomonaga, but I will assign him to E. Most theorists belong to H or E. But, when it comes to contrasting Yukawa and Tomonaga, it may be appropriate to use the analogy to designer vs. craftsman.

Kamefuchi's type II and type III seem to correspond to Nambu's H mode and E mode, respectively. However, when we consider the corresponding categories identical, it causes inconsistency between Kamefuchi's and Nambu's classification of Yukawa and Tomonaga. The inconsistency comes from the difference in the viewpoint between Kamefuchi and Nambu. Namely, Kamefuchi attach importance on the physicist's preference of a method, especially for the classification of Yukawa, and Nambu, on the physicist's successful work.

On the other hand, Kamefuchi's type II and type III seem to correspond to Nambu's category of craftsman and that of designer, respectively. In this case, we can regard the corresponding categories as nearly equal without causing inconsistency between Kamefuchi's and Nambu's classification of the two physicists. The consistency in this case arises because Nambu's classification here is based on methodology of the physicists, similarly to Kamefuchi's.

  1. S. Kamefuchi, Tosho No. 766, p. 2 (December, 2012) in Japanese.
  2. English translation has been obtained from: Antonio Gramsci, Selections from the Prison Notebooks, edited and translated by Q. Hoare and G. N. Smith, p. 767 (ElecBook, London, 1999).
  3. Y. Nambu, The Legacies of Yukawa and Tomonaga, AAPPS Bulletin Vol. 18, No. 6, p. 7 (2008)


  1. Hi Prof. Ted, actually I'm not sure which type is more appropriate for Dr. Yukawa and Tomonaga. As you know, Yukawa had native preference to natural philosophy and Tomonaga was very good at mathematics like Dr. Heisenberg. Indeed, according to his book ' The Part and The Whole ' , Heisenberg was also found in deep philosophical tendency. So, in my opinion, Yukawa would be categorized to designer or type(III), while Tomonaga to craftsman, but type(III) as well. Because I consider Heisenberg or Dirac as not only craftsmen but also a sort of Pythagoreans who originated from a natural philosopher.

  2. Hayakawa-san, thanks for your kind and illuminating comment. The single physicist who has done a great job actually has multiple facets. Therefore, classification of physicists should be made by defining the viewpoint clearly. If we look at the long-term attitude of study, not only Yukawa but also Tomonaga, Heisenberg and Dirac were philosophical, as you noted. By the way, I liked Heisenberg's Der Teil und das Ganze very much and read it both in Japanese and English translations (the title of the latter is Physics and Beyond). I bought even a German edition but have not read it yet.