Pascual Jordan

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Pascual Jordan in the 1920s

Ernst Pascual Jordan (born October 18, 1902 in Hanover ; † July 31, 1980 in Hamburg ) was a German theoretical physicist and politician.

Pascual Jordan played a key role in the development and mathematical formulation of quantum mechanics . In addition, his work established the quantum field theory .


Ernst Pascual Jordan was the son of the painter Ernst Pasqual Jordan . Its name is derived from his Spanish ancestor Pascual Jorda, who settled in Hanover after the Napoleonic Wars . Pascual Jordan studied after high school on the Bismarck Real reform school in Hanover from 1921 Mathematics , Physics and Zoology at the Technical University of Hanover and in 1923 at the University of Göttingen , where he in 1924 Max Born doctorate was.

He then worked with Max Born, then director of the department for theoretical physics, and his assistant Werner Heisenberg . The three published their groundbreaking results in 1925 in two essays on quantum mechanics .

The mathematical formulation came mainly from Jordan, who had previously been Richard Courant's assistant . At this time, Jordan also wrote a book with James Franck, Stimulating quantum leaps through shocks , Springer, Berlin 1926.

After his habilitation in 1926 on the subject of the theory of quantum radiation , he first became a private lecturer in Hamburg the following year and then received an extraordinary professorship at the University of Rostock in 1929 . In 1935 he was appointed to the chair for theoretical physics there.

In 1933 Jordan became a member of the NSDAP and the SA . Despite his nationalist attitudes, he rejected movements such as Deutsche Physik . In his popular science book The Physics of the 20th Century , published in 1936, he expressly paid tribute to the achievements of Jewish physicists. He even tried to convince the National Socialists that modern physics was the best remedy against communism.

Nancy Greenspan writes in her biography of Max Born, Jordan was one of the few visitors by James Franck and Max Born after Franck's ostentatious resignation at the seizure of power by the Nazis in 1933 was - he was very upset about his treatment, the threat of dismissal and by Born and expressed to this, he himself might have been able to prevent this if he had been a member of the NSDAP. A few days later he joined this.

His advocacy of National Socialism apparently did not bring him any advantages for his career. He even seemed to be distrusted. So he was not involved in important war projects. From 1939 he worked as a meteorologist in the Air Force, then in a physics institute in the Navy. In 1944, with Werner Heisenberg's support, he succeeded Max von Laue as full professor at the Humboldt University .

After the end of the Second World War and the National Socialist rule, his political behavior initially prevented academic activity. Only after denazification in 1947 did he initially receive a visiting professorship in Hamburg on the recommendation of Wolfgang Pauli . In 1953 he became a full professor there until his retirement in 1971.

Pascual Jordan grave , Ohlsdorf cemetery

When Pauli asked him why he could write “things like that” in the “Third Reich”, he only replied why Pauli had read them. His involvement in National Socialism was probably the reason why he was the only one of the founders of quantum mechanics and quantum field theory to not receive a Nobel Prize. For Schweber he was a "... tragic unsung hero of quantum field theory". Albert Einstein proposed him twice in the mid-1920s and Eugene Wigner in 1979.

From 1957 to 1961 Jordan was a member of the German Bundestag for the CDU . His negative opinion in 1957 against the Göttingen eighteen (and thus also against Born and Heisenberg) on ​​the question of the nuclear armament of the Bundeswehr was remarkable . The fact that he denied his academic teacher Max Born the ability to make political judgments led to a falling out between the two.

Jordan was a co-founder of the right-wing conservative Evangelical Emergency Community in Germany (ENiD), which was formed in 1966 . He was also an important member of the Brotherly Circle for many years , but left it after a falling out in the 1960s.

Pascual Jordan's grave is on the Ohlsdorf cemetery in Hamburg, grid square E 9 (southwest of chapel 4).

Scientific work

Together with Max Born, Pascual Jordan expanded Heisenberg's novel ideas into the consistent mathematical formalism of matrix mechanics in 1925 . Among other things, he proved the fundamental commutation rules of quantum mechanics established by Max Born (for example between the momentum operator and the position operator). Independently of Paul AM Dirac , he set up the transformation theory, a more abstract formulation of quantum mechanics.

In 1927 he laid the foundations for quantum field theory , which he expanded the following year in work with Oskar Klein , Eugene Wigner and Wolfgang Pauli .

While looking for an extension of the quantum mechanical formalism, he found a mathematical structure that has been known since then as Jordan algebra and founded a new branch of algebra. Its actual goal was a quantum mechanical formalism that was largely independent of the concepts of classical physics.

He also found the Fermi-Dirac statistics (which he called Pauli statistics) in 1925 at the same time or even before Enrico Fermi and Paul Dirac ; However, the manuscript was misplaced by Max Born for six months, so that it was too late for publication. Max Born reports on this in his autobiography and therefore felt guilty towards Jordan all his life.

In the mid-1930s, he turned away from quantum field theory and turned to biology . His attempts to apply quantum theory here too ultimately proved unsuccessful. In his opinion there was a mechanism somewhere in the cell that could amplify random quantum events and transform them into macroscopic processes. In the experiments of the X-ray irradiation of cells of the genetics of the time he tried to get on the track. One of Jordan’s motives was probably to use quantum mechanics to overcome the determinism of classical physics in explaining life.

In the post-war period , his work focused on the general theory of relativity , which was ostracized under National Socialism, and related topics ( cosmology , gravitational physics ). He made an important contribution to the re-establishment of this research area in Germany at a high level (his students were among others Engelbert Schücking , Wolfgang Kundt and Jürgen Ehlers ). He himself worked on an idea by Paul Dirac about a time-varying gravitation constant as part of a scalar tensor theory, which he developed in the 1940s and which he presented in 1952 in his book Gravity and Universe . A similar theory ( Brans-Dicke-Theory ) was later formulated by Carl H. Brans and Robert Dicke , the focus of their consideration being on the implementation of Mach's principle . He explained the continental drift as a consequence of an expanding globe ( expansion theory ). This declaration is now considered refuted.

In Hamburg he gave many popular science lectures and since the 1930s has written several books aimed at a broad readership.

Jordan was awarded the Max Planck Medal (1942), the Carl Friedrich Gauß Medal (1955), the Gravity Research Foundation Prize in New Boston (1967) and the Konrad Adenauer Prize for his scientific achievements Germany Foundation (1970) awarded. From 1963 to 1967 he was President of the Academy of Sciences and Literature Mainz .

In his essay The ideological significance of modern physics , he comes to the conclusion that materialistic natural philosophy is in contradiction to scientific knowledge.

Works (selection)

  • with Max Born Elementare Quantenmechanik , Springer Verlag 1930
  • with James Franck suggestion of quantum leaps through impacts , Springer Verlag 1926
  • Statistical mechanics based on quantum theory , Vieweg 1933, 2nd edition 1944
  • Descriptive quantum theory: an introduction to the modern conception of quantum phenomena , Springer Verlag 1936
  • The Physics of the 20th Century , Vieweg 1936, 8th edition 1949, English edition, New York 1944
    • New editions under Atom and Space: Introduction to the Thoughts of Modern Physics , Vieweg 1956, 1960
  • The physics and the mystery of organic life. 1941.
  • The origin of the stars. Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart 1947.
  • The origin of protein life. In: Wolfgang Dennert (ed.): Nature - the miracle of God. Bonn 1950.
  • Research makes history. Vittorio Klostermann, Frankfurt am Main 1954
  • Gravity and Universe: Foundations of Theoretical Cosmology Vieweg 1952 (revised 1955).
  • The picture of modern physics. Stromverlag, Hamburg-Bergedorf 1947, Ullstein 1957
  • What will the world of tomorrow look like? Paul List Verlag, Munich 1958
  • The scientist before the religious question . 1963, Quell Verlag 1989
  • The expansion of the earth: Conclusions from Dirac's gravitational hypothesis , Vieweg 1966 (English translation The expanding earth , Oxford, Pergamon Press 1971)
  • Albert Einstein , Frauenfeld, Stuttgart 1969
  • Creation and Mystery. Answers from a scientific point of view , Stalling Verlag 1970
  • Knowledge and reflection , Stalling Verlag 1972
  • Encounters , Stalling Verlag 1976
  • The ideological significance of modern physics . Munich: Klinger Verlag 1971
  • Early Years of Quantum Mechanics: Some Reminiscences. In: Mehra: The Physicists Concept of Nature. Reidel, 1973.
  • Pascual Jordan The early years of quantum mechanics - memories , Phys. Blätter, March 1975 (originally in Jagdish Mehra (Ed.) The physicists concept of nature , Reidel 1973)
  • On the future of physics , Phys. Blätter, November 1970, online
  • Results and problems of the extended theory of gravity , Phys. Sheets, December 1954, online
  • Dirac hypothesis and earth expansion , Phys. Leaves, October 1966, online

Works by Pascual Jordan online:

See also


Web links

Commons : Pascual Jordan  - Collection of Images

Individual evidence

  1. ^ Klaus Mlynek: Jordan, (1) Ernst Pascual. In: Hannoversches Biographisches Lexikon (see section "Literature")
  2. M. Born, P. Jordan: To quantum mechanics. In: Journal of Physics. Volume 34, 1925, p. 858
  3. ^ M. Born, W. Heisenberg, P. Jordan: Zur Quantenmechanik II. In: Zeitschrift für Physik , Volume 35, 1926, p. 557
  4. ^ Greenspan Max Born , Spectrum Verlag 2005, p. 187
  5. Schuecking. Physics Today , 1999, No. 10
  6. Bert Schroer: Pascual Jordan, his contributions to quantum mechanics and his legacy in contemporary local quantum physics , 2003, p. 4 (see web links)
  7. Celebrity Graves
  8. P. Jordan: About a new foundation of quantum mechanics I. In: Journal for Physics. Volume 40, 1926, p. 809
  9. P. Jordan: About a new foundation of quantum mechanics II. In: Journal for Physics. Volume 41, 1927, p. 797
  10. P. Jordan: About waves and corpuscles in quantum mechanics. In: Journal of Physics. Volume 45, 1927, p. 765
  11. P. Jordan, O. Klein: To the multi-body problem in quantum theory. In: Journal of Physics. Volume 45, 1927, p. 75
  12. P. Jordan, E. Wigner: About the Paulische Äquivalenzverbot. In: Journal of Physics. Volume 47, 1928, p. 631
  13. W. Pauli, P. Jordan: On the quantum electrodynamics of charge-free fields. In: Journal of Physics. Volume 47, 1928, p. 151
  14. P. Jordan: About the multiplication of quantum mechanical quantities I. In: Zeitschrift für Physik. Volume 80, 1933, p. 285
  15. P. Jordan: About the multiplication of quantum mechanical quantities II. In: Zeitschrift für Physik. Volume 87, 1934, p. 505
  16. P. Jordan, J. von Neumann, E. Wigner: On the algebraic generalization of the quantum mechanical formalism. In: Annals of Mathematics Princeton. Volume 35, 1934, p. 29
  17. Schücking: Jordan, Pauli, Politics, Brecht and a variable gravitational constant. In: Physics Today. Volume 52, 1999, Issue 10
  18. Ehlers, Schuecking: But Jordan was the first. In: Physics Journal. Volume 1, 2002, issue 11
  19. Brans: The roots of scalar tensor theory , 2005, arxiv : gr-qc / 0506063v1
  20. An example: he wrote the introduction to the and probably also had editorial responsibility for the chapter “Physicists” in the collection Researchers and Scientists in Today's Europe , Series Designers of Our Time. Volume 3, edited by Hans Schwerte (pseud.) And Wilhelm Spengler . Stalling, Oldenburg 1958. Pascual Jordan's introduction: Physics in the 20th century. Pp. 15–37, with a focus on atomic physics.