Wednesday, January 11, 2023

Mystery of the Dream and the Memory

"The Theory of Atomic Spectra" by E. U. Condon & George H. Shortley, taken from the Web site of Amazon (https://www.amazon.com/Theory-Atomic-Spectra-U-Condon/dp/0521092094/)

The memory about the book I hadn't remembered for decades suddenly appeared in my dream the night before last as the names of two co-authors, "Condon–Shortley." Even after waking up, I couldn't remember its title but thought it was probably a book about condensed matter physics. Searching the authors' names on the Internet, I found it to be a masterpiece, "The Theory of Atomic Spectra," published in 1935 [Note 1]. We can divide physics into two subfields: physics on condensed matter and that on particles and nuclei. Physics on atomic spectra belongs to the former. So, my thought was correct.

My university student days were soon after World War II and in a period of confusion, and many pirated editions of masterpieces about various topics in physics appeared in Japan. An upper-year student with a part-time job related to pirated edition publishers would often come to our classroom to advertise those editions. Once, he might have said about the bootleg version of this book, "Condon–Shortley is coming out. It's a classic book on the theory of atomic spectra." During a lecture on atomic spectra, the teacher might have said, "You can learn more about this in Condon–Shortley book." Further, I may have heard one of my classmates say, "I'm not sure if I should buy Condon–Shortley."

I majored in "atomic nuclei" and had no interest in "atomic spectra." So, I have neither wanted to read that book nor remembered it for more than 65 years after graduation. Nonetheless, I recalled the authors' names in a dream. Such is an extremely curious and mysterious phenomenon.

Notes
  1. On the publisher's website, it reads: When first published, a reviewer in Nature said that 'Its power and thoroughness leave the general impression of a work of the first rank, which successfully unifies the existing state of our knowledge, and will prove for many years a starting point for further researches and an inspiration to those who may undertake them.'
    (https://www.cambridge.org/jp/academic/subjects/physics/atomic-physics-molecular-physics-and-chemical-physics/theory-atomic-spectra)

Sunday, December 06, 2020

On Kamefuchi's Essay about Heisenberg and Yukawa (6)

References [25–28] of this article.

4 Different methods of theoretical physics research

Kamefuchi divides the methods of theoretical physics research into the "ascending type" and the "descending type" to explain why Heisenberg's and Yukawa's later studies were unfinished. In the "ascending type," the researcher "builds up the theory from the basic points." In the "descending type," he or she "sets a hypothetical principle at a high level far beyond the existing theoretical system and descends from there to try to deduce all the laws of physics. Kamefuchi adds, "In the latter method, one has to rely on intuition or analogy. Neither of these has objectivity or inevitability. So, mostly one goes astray." He then infers: Both Heisenberg and Yukawa achieved results by the former method in the first half of their career. However, they turned to the latter type in the second half, failing to complete the research.

Yoichiro Nambu also described a similar classification of research methods [25, 26]. Kamefuchi thinks that the research method can change between the first and the second half for one researcher. On the other hand, Nambu names them by the proper name of famous physicists as if a researcher uses a single method throughout his or her life. However, we should understand each of them to be the one related to the representative, successful research done by the physicist used for the naming. Nambu calls his categories "Yukawa mode" and "Dirac mode" in [25]. As an explanation, I will introduce a concise one in the book by Michio Kaku and Jennifer Thompson [27].
The Yukawa mode is deeply rooted in experimental data. Yukawa was led to his seminal idea of the meson as the carrier of the nuclear force by closely analyzing the data available to him. The Dirac mode, however, is the wild, speculative leap in mathematical logic that led to astonishing discoveries, such as Dirac's theory of antimatter or his theory of the monopole [...]. Einstein's theory of general relativity would fit into the Dirac mode. ([27] p. 85)

Later, Nambu modified this and divided his classification into three types. [26] The explanation for each is as follows.
  • Einstein mode (top-down): To create a theory by assuming that "nature should follow this principle." Example: Einstein's theory of gravity (general theory of relativity), made under the assumption that "in general, space may be curved."
  • Yukawa mode (bottom-up): To start from the working assumption that "behind the new phenomenon, there is some new field or particle, apart from deep reasons." Examples: Yukawa's meson theory and Pauli's neutrino hypothesis.
  • Dirac mode (from heaven): To assume that a mathematically beautiful theory should be true. Examples: Dirac's monopole theory, supersymmetry theory, and string theory, currently being explored.
Einstein's general theory of relativity, which was an example of the Dirac type at the stage of literature [25], was promoted to the independent one. As a result, the Einstein type (top-down) and the Yukawa type (bottom-up) have become equivalent to Kamefuchi's "descending type" and "ascending type," respectively. Nambu states about the examples of Dirac-type as follows. 'The existence of the monopole is now the natural consequence of the quantum field theory, but we still need to confirm it by observation. Studies of supersymmetry and string theories are currently in full swing, so we can say that it is "the heyday of Dirac mode" nowadays.' However, the success or failure of these theories is still unclear, and it is interesting to keep an eye on what a future comes for the high energy physics theory.

By the way, I wonder if Einstein's general theory of relativity is entirely top-down. This is because it is known that there was a thought experiment at the starting point for him to come up with this theory as quoted by Holton ([28], p. 78): "For him, at least in the vicinity, there is no gravitational field during the fall, for example, given an observer who falls freely from the roof." Kamefuchi does not state that Einstein's mode of thinking had been top-down since the time of the general theory of relativity. Instead, he writes that Einstein also turned to the use of the top-down method in the 30 years of his later life for trying unsuccessfully to unify the gravitational and electromagnetic fields.

Here I would like to add the story in Kaku and Thompson's book [27] that Nambu's friends named a type that combines the first two classifications by Nambu "Nambu Mode." They made this naming in commemoration of Nambu's 65th birthday (1985). I quote the related part below.
[...] This mode combines the best features of both modes of thinking and tries carefully to interprete the experimental data by proposing imaginative, brilliant, and even wild mathematics. The superstring theory owes much of its origin to the Nambu mode of thinking.
Perhaps some of Nambu's style can be traced to the clash of Eastern and Western influences represented by his grandfather and father. [...] ([27] p. 85)

Acknowledgement

I heartily thank Naoki Toyota, Professor Emeritus, Tohoku University, for his telling me that there is a story in Ref. [10] that Bohr criticized Pauli's lecture as well as for his other useful suggestions provided by email exchanges on the topic of this article.


References
  1. Y. Nambu, "Direction of particle physics," in Proc. Kyoto Int. Symp.: The Jubilee of the Meson Theory, Kyoto, Aug. 15–17, 1985, edited by M. Bando, R. Kawabe, and N. Nakanishi; Prog. Theor. Phys. Suppl. No. 85, 104 (1985).
  2. Y. Nambu, One Hundred Years of Elementary Particle Physics (International Institute for Advanced Studies, Kizugawa, Kyoto Prefect., 2000) in Japanese.
  3. M. Kaku and J. Thompson, Beyond Einstein: The Cosmic Quest for the Theory of the Universe (Oxford University Press, Oxford, N. Y., 1997; first edition, Bantam, 1987).
  4. G. Holton, "What, precisely, is "thinking"? ...Einstein's answer," in Einstein, History, and Other Passions (AIP Press, Woodbury, 1995) p. 74. [See also "On trying to understand scientific genius," in Thematic Origins of Scientific Thought: Kepler to Einstein, Revised edition (Harvard University Press, Cambridge, Mass., 1988) p. 371.]
(End)
Search word: Kamefuchi-2020

Thursday, October 22, 2020

On Kamefuchi's Essay about Heisenberg and Yukawa (5)

References [15, 18, 22] of this article.

3 Yukawa's tragedy

3.1 Yukawa's research at that time

Kamefuchi writes, "The lectures progressed, and Yukawa called up K's name for the presentation of his paper co-authored with collaborator K, "Space-time picture of elementary particles." K is Yasuhisa Katayama (1926–1978), familiar to those who know about Yukawa's later studies (as for the bibliographic information of the paper published in the proceedings, see Ref. [3] given in the first part of this article). This research belongs to the work of elementary domain theory that Yukawa worked on with coworkers in his later years. About this work, Yukawa writes in the "Preface" of Ref. [15], "I was able to formulate a theory in 1967 with the great efforts of Mr. Yasuhisa Katayama." Yukawa continued somewhat proudly, "The following year, I was able to publish a paper co-authored with Katayama and a paper with the additional coworker, Umemura." These papers are Refs. [16] and [17].

Three years later, Yukawa wrote Preface and "Part V Unified Theory of Elementary Particles" as the supervisor of Ref. [18]. In them, he frankly writes the reaction of academia to the theory of elementary domains and his own thought as follows:
In Part V, we decided to follow a path towards a unified theory. It will not be the only way, nor is it guaranteed to reach its goal. On the contrary, it is the path that many researchers consider to be the largest deviation from the legitimate one. ([18], Preface, p. vii)
If we proceed in this direction, we may, in the end, have to run into the problem of the quantization of space-time itself in some sense. The concept of the elementary domain itself may still be incomplete in that it assumes the Minkowski space behind it as a four-dimensional continuum. However, all the elucidation remains in the future. ([18] Part V, p. 608–609)

3.2 Impact and evaluation of Yukawa's research at that time

Looking up the number of citations of papers [16] and [17] by Yukawa and his coworkers on Google Scholar, we find the number 46 only for [17]. I have noticed from the number of citations of my own papers that Google Scholar's statistics are inaccurate. For example, if there are similar titles, they are sometimes wrongly regarded as the same paper. Therefore, for [16] and [17], I would like to use, instead of Google Scholar's, the numbers in the journal Progress of Theoretical Physics and at the Crossref site linked to it. Using the sum of the number of citations from these two sources (no duplication of citing papers between the two), it is 39 for [16] and 28 for [17]. Compared to Yukawa's Nobel Prize-winning paper [19], which has more than 2,400 citations (according to Google Scholar), the former numbers are small. However, there might be a possibility that Yukawa's work on the elementary domain will make new contributions to the development of particle theory in the future. I would like to quote an experts' view on this point.

Nicholas Kemmer (1911–1998), who was a Russian-born nuclear physicist working in Britain, described Yukawa's research after the 1940s in reference [20] as follows.
Yukawa devoted the greater part of his subsequent life as a research worker to the quest for a better, deeper fundamental theory. He published over twenty papers spanning a period of twenty years developing various approaches to this goal. Central to his thinking was the belief that the association of any elementary particle with a single geometrical point in space was in some deep sense mistaken; the key concept in many of his publications is the 'non-local field'. [...] We cannot see into the future and say with confidence that all the ideas presented in these papers are lacking in any grains of deeper truth that we do not yet perceive. And we cannot measure the stimulation that readers of his papers on the way to developing ideas of their own may have received. Even so it is a fact that in present day work one would be hard put to find reference to or influence of his later publications.
Kemmer's words are a modest statement that Yukawa's second half research was barren.

Professor Emeritus Laurie Brown, who is an American theoretical physicist and historian on quantum field theory and particle physics, stated in Ref. [21] as follows.
The idea of nonlocal fields (which is to be distinguished from the idea of local fields having nonlocal interaction) gradually became a theory of elementary particles with internal structure. By the late 1960’s it was superseded by Yukawa’s concept of "elementary domain", based upon the quantization of the classical continuously deformable body. These fundamental ideas do not play a major role in current theoretical physics but may well be vindicated in a future physics.
Here, the last words after "but" give Yukawa fans (I am one of them) hopes for the future. However, Brown, similarly to Kemmer, seems to have added these words in honor of Yukawa, who had established meson theory and the method of particle physics at a young age.

Sho Tanaka (1928–2019), a particle physicist and emeritus professor at Kyoto University, introduces Japanese-born researchers' evaluation of Yukawa's postwar research together with his own views [22]. Here, I would like to quote Yoichiro Nambu's words about "Dr. Yukawa's postwar research activities," which seem to be the outspoken and sharpest criticism.
Unfortunately, [Yukawa's postwar research] was not very fruitful. Aside from the relentless efforts he made to understand elementary particles as things with a geometric spread, the content and method seem to have been too naive. With the development of the gauge field theory, the geometrical view has become very important, and there is a possibility that the internal quantum numbers may be reduced to geometry. However, it cannot be said that his idea was a seed of these developments. The influence he had on younger Japanese scholars since the theory of mesons was more indirect. (Quoted from [23]; [22] p. 311)
Tanaka himself points out in Ref. [24] that the D0 brane of string theory is close to the idea of ​​Yukawa's elementary domain. However, this may be one of the developments that Nambu considers as independent of Yukawa's idea.

Next time, I would like to think about different research styles of theoretical physics in connection with Kamefuchi's thought about the common reason why the research of Heisenberg and Yukawa around the time of the "tragedy" ended unfinished.

References
  1. H. Yukawa, Hideki Yukawa Self-Selected Works Vo. 2 (Asahi Shimbun, Tokyo, 1971) in Japanese.
  2. Y. Katayama and H. Yukawa, "Field theory of elementary domains and particles. I," Prog. Theor. Phys. Suppl., 41, 1 (1968).
  3. Y. Katayama, I. Umemura, and H. Yukawa, "Field theory of elementary domains and particles. II," Prog. Theor. Phys. Suppl., 41, 22 (1968).
  4. H. Yukawa, supervisor, Iwanami Lectures: Basics of Modern Physics Vol. 11, Elementary Particle Theory (Iwanami, Tokyo, 1974) in Japanese.
  5. H. Yukawa, "On the interaction of elementary particles. I," Proc. Phys.–Math. Soc. Japan (3) 17, 48 (1935).
  6. N. Kemmer, "Hideki Yukawa. 23 January 1907–8 September 1981," Biographical Memoirs of Fellows of the Royal Society, 29, 661 (1983). JSTOR, https://www.jstor.org/stable/769816. Accessed July 30, 2020.
  7. L. M. Brown, "Yukawa, Hideki," in Complete Dictionary of Scientific Biography (Charles Scribner's Sons, New York, 2008); online version of this article available at
    https://www.encyclopedia.com/people/science-and-technology/physics-biographies/hideki-yukawa. Accessed July 31, 2020.
  8. S. Tanaka, Hideki Yukawa and Einstein (Iwanami, Tokyo, 2008) in Japanese.
  9. Y. Nambu, "Dr. Yukawa and Physics in Japan," Kagaku 52, No. 2 (1982) in Japanese.
  10. S. Tanaka, "From Yukawa to M-theory," in Proc. Int. Symposium on Hadron Spectroscopy, Chiral Symmetry and Relativistic Description of Bound Systems, Nihon Daigaku Kaikan, Feb. 24-26, 2003; KEK Proceedings 2003-7, edited by S. Ishida et al. (KEK, Tsukuba, 2003) p. 3; also available as arXiv:hep-th/0306047.
(To be continued)
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Search word: Kamefuchi-2020

Friday, October 09, 2020

On Kamefuchi's Essay about Heisenberg and Yukawa (4)

Reference [12] of this article.

2 Heisenberg's tragedy (continued)

2.6 Impact of Heisenberg's research at that time

About the research of Heisenberg and Yukawa at the time of the event mentioned in the essay, Kamefuchi wrote, "Unfortunately, both the studies were unfinished." I'll write later about what he wrote as a common reason for the incompleteness of them. Even though Heisenberg's research at that time was incomplete in itself, the concepts used in it seems to have had a considerable positive effect on other researchers. Concerning this, I would like to quote the description by Professor Cao of Boston University, who specializes in the history of science.
 At the 1958 Rochester Conference on high-energy nuclear physics held in Geneva, Heisenberg invoked the idea of a degenerate vacuum to account for internal quantum numbers, such as isospin and strangeness, that provide selection rules for elementary particle interactions (1958).*
 In an influential paper submitted in 1959,** Heisenberg and his collaborators used his concept of a degenerate vacuum in QFT [quantum field theory] to explain the breaking of isospin symmetry by electromagnetism and weak interactions. [...]
 Heisenberg's degenerate vacuum was at the time widely discussed at international conferences. It was frequently quoted, greatly influenced field theorists, and helped to clear the way for the extension of SSB [spontaneous symmetry breaking] from hydrodynamics and condensed matter theory to QFT. ([12] p. 283)
The word "degenerate vacuum" that appears many times in the above quote is closely related to the SSB (spontaneous symmetry breaking) in the last sentence. The reference cited at the place of the symbol * is the reference [2] in Part 1 of the present article, and the paper cited at ** is the reference [8] in Part 2. The former is the lecture of "Tragedy" published in the proceedings, and the latter is the paper published later in collaboration with young researchers.

By the way, if you look up the number of citations of these papers on Google Scholar, it is 16 for the former and 226 for the latter. Cao uses the words "frequently quoted" for Heisenberg's work at the time. However, the above citation numbers are much smaller than those of Heisenberg's famous papers. Namely, the citation number for the Nobel Prize-winning paper on the formulation of quantum mechanics based on matrices [13] is 1709, and that for the work on the uncertainty principle [14] is 4697. (All the citation numbers are as of July 27, 2020.) The reason for the small citation numbers for the research during the period of "tragedy" seems that it did not succeed as the whole concept.

Speaking of the application of SSB to particle physics, I remember that the reason for receiving the Nobel Prize by Yoichiro Nambu was "discovery of the mechanism of SSB in particle physics." So, I have thought that it was almost Nambu's originality. However, in fact, Heisenberg's research had an impact on Nambu. About this, I make here a bit long quote from Cao's book (numbers representing Nambu's papers cited are omitted).
 Nambu's work on superconductivity led him to consider the possible application to particle physics of the idea of non-invariant solutions (especially in the vacuum state). [...]
 [...]
 [...]
 It is of interest to note the impact of Dirac and Heisenberg on Nambu's pursuing this analogy. First, Nambu took Dirac's idea of holes very seriously and viewed the vacuum not as a void but as a plenum packed with many virtual degrees of freedom. This plenum view of the vacuum made it possible for Nambu to accept Heisenberg's concept of degeneracy of the vacuum, which lay at the heart of SSB. Second, Nambu was trying to construct a composite particle model and chose Heisenberg's non-linear model, 'because the mathematical aspect of symmetry breaking could be mostly demonstrated there', although he never liked the theory or took it seriously.

Next time, I would like to write about a paper related to "tragedy" in the case of Yukawa.

References
  1. T. Y. Cao, Conceptual Developments of 20th Century Field Theories, (Cambridge University Press, Cambridge, 1997; second edition available, 2019).
  2. W. Heisenberg, Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen, Z. Physik 33, 879 (1925).
  3. W. Heisenberg, Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik, Z. Physik 43, 172 (1927).
(To be continued)
Last modified Jan 22, 2021.

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Thursday, September 17, 2020

On Kamefuchi's Essay about Heisenberg and Yukawa (3)

References [9, 10, 11] of this article

2 Heisenberg's tragedy (continued)

2.5 Reasons for Pauli's Rebellion

Kamefuchi writes, "Pauli was a close friend of Heisenberg's since student days and coworker of this problem until three months ago. Why did he go on such outrage in a place where prominent researchers in particle physics lined up?"

Here are the words "three months ago." These probably come from the fact that Pauli had been to the United States for three months before this international conference. However, Pauli departed for the United States, according to Heisenberg's autobiography [8], a week plus a few weeks after Christmas 1957, namely around late January 1958. Thus, the duration from this time of departure to the international conference should be about five months.

Kamefuchi then provides an answer to the above question of his own by quoting the explanation (the part in the quotation marks below) given to him later by Professor K. Broiler (at the University of Bonn) and attaching a little suspicious comment.
"In the United States, Pauli perhaps proudly spoke about their research but got strong objections from young American geniuses to come to think that it was a difficult job. Thus, he would have wanted openly to express to the excellent people at the conference that he no longer believed in their own theory." This seems to mean that Pauli sacrificed his friend's honor for his own ...
Broiler's explanation is a presumption, but there is a document [9] (this reference is academic, unlike Polkinghorne's book, and the following quote is in a footnote) that assertively states a similar thing as follows.
Although Pauli drafted the first preprint, entitled 'On the Isospin Group in the Theory of the Elementary Particles,' he withdrew from further collaboration in January 1958, after he encountered severe criticism and opposition to the theory from the U.S. physicists at the American Physical society meeting in New York; thus Heisenberg was left to work out the details of the theory with younger collaborators (Dürr et al., 1959). ([9] p. 1120)
The reference "Dürr et al., 1959" at the end of the above quote looks like the source of this entire description but is not such. It is the paper (also mentioned in the previous part of the present series as Ref. [8]) of the result of Heisenberg's continued research with young collaborators. Thus, the quote does not specify the source that Pauli received severe criticism from the U.S. physicists. However, it hints that the time of Pauli's decision to withdraw from the joint research with Heisenberg was early in the period of his visit to the United States."

By the way, there was an important person who severely criticized Pauli's lecture in the United States besides American physicists. In a collection of essays [10] by Freeman Dyson, an American theoretical physicist and mathematician born in England, we find this description:
Pauli happened to be passing through New York, and was prevailed upon to give a lecture explaining the new idea [of Heisenberg and Pauli] to an audience that included Niels Bohr, who had been mentor to both Heisenberg and Pauli [...]. Pauli spoke for an hour, and then there was a general discussion during which he was criticized sharply by the younger generation. Finally, Bohr was called on to make a speech summing up the argument. "We are all agreed," he said, "that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough." ([10] pp. 105-106)
The statement here that Pauli "was criticized sharply by the younger generation" underscores Broiler's presumption as well as the description in Ref. [9]. Moreover, Pauli's teacher, Niels Bohr, criticized Pauli. It is a little difficult to understand that Bohr's words, "Not crazy enough," are a harsh criticism. Dyson adds the following explanation in his next paragraph (I tried to shorten it, only finding that Dyson's text was like a polished jewel and that it was impossible to do so).
When the great innovation appears, it will almost certainly be in a muddled, incomplete, and confusing form. To the discoverer himself it will be only half-understood. To every body else it will be a mystery. For any speculation that does not at first glance look crazy, there is no hope. ([10] p. 106)
Concerning Pauli's withdrawal from the joint research with Heisenberg, the former wrote to the latter during the former's stay in the United States. This is described in Heisenberg's autobiography [11] as follows (Wolfgang in the quotation refers to Pauli):
Then we were divided by the Atlantic, and Wolfgang's letters came at greater and greater intervals. [...] Then, quite suddenly, he wrote me a somewhat brusque letter in which he informed me of his decision to withdraw from both the work and the publication [of our common project]. ([11] p. 235)
This story is in a chapter "The Unified Field Theory" of the autobiography, concluding by the following sentence:
Toward the end of 1958 I received the sad news that he [Wolfgang] had died after a sudden operation. I cannot doubt but that the beginning of his illness coincided with those unhappy days in which he lost hope in the speedy completion of our theory of elementary particles. I do not, of course, resume to judge which was the cause and which the effect. ([11] p. 236)
If you read the above statement only, you would feel sad. However, as Kamefuchi mentioned referring to the Japanese translation of Heisenberg's autobiography, there was the following facts. "A few weeks after the meeting, both of them were invited guests at a summer school in Varenna on Lake Como, Italy. Pauli was friendly to Heisenberg at that time." Also there, Pauli said to Heisenberg, "I think you are doing right to continue working on these problems. As for me, I have to drop out. ..." These give us a feeling of relief.

How important was Heisenberg's research at that time in the subsequent progress of theoretical physics? I would like to start the next part with such a story.

References
  1. H. P. Dürr, W. Heisenberg, H. Mitter, S. Schlieder, and K. Yamazaki, "Zur Theorie der Elementarteilchen," Z. Naturf. 14a, 441 (1959).
  2. J. Mehra and H. Rechenberg, The Historical Development of Quantum Theory, Volume 6, Part 2 (Springer, New York, 2001). [Note: I happened to have this book because I was attending the "Hideki Yukawa Study Group," once held at the Osaka Science Museum, and thought that it might be useful for discussions there.]
  3. F. Dyson, From Eros to Gaia (Penguin, London, 1993; first published by Pantheon, New York, 1992). [Note: When I was still working, I recommended this book to my colleague Naoki Toyoda (currently Professor Emeritus of Tohoku University). This time I emailed him about the topics related to the present article. Then, he taught me back the presence in this book of the part quoted in the text.]
  4. W. Heisenberg, Physics and Beyond: Encounters and Conversations, translated from German by A. J. Pomerans (Harper & Row, New York, 1972); original German edition, Der Teil und das Ganze: Gespräche im Umkreis der Atomphysik (R. Piper, Munich, 1969); Japanese version, Bubun to Zentai, translated by K. Yamazaki (Misuzu-Shobo, Tokyo, 1974; new edition 1999).
(To be continued)
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