Wilhelm Lenz (February 8, 1888 in Frankfurt am Main – April 30, 1957 in Hamburg) was a German physicist, most notable for his invention of the Ising model[1] and for his application of the Laplace–Runge–Lenz vector to the old quantum mechanical treatment of hydrogen-like atoms.[2]

Biography

In 1906, Lenz graduated from the Klinger-Oberralschule, a non-classical secondary school in Frankfurt, and went to study mathematics and physics at the University of Göttingen. From 1908 to 1911, Lenz studied under Arnold Sommerfeld, at the University of Munich, and he was granted his doctorate[3] on March 2, 1911. Upon graduation, he stayed on at the University, became Sommerfeld’s assistant on April 1, 1911, and he completed his Habilitation on February 20, 1914, becoming a Privatdozent on April 4, 1914. During World War I, he served as a radio operator in France and was awarded the Iron Cross Second Class in 1916. From September 30, 1920, he was again an assistant to Sommerfeld at the University of Munich’s Institute of Theoretical Physics, and he was appointed to the title and rank of extraordinarius professor at the University, on November 11, 1920. On December 1, 1920 he became an extraordinarius professor at the University of Rostock. From 1921, until his retirement in 1956, he was at the University of Hamburg, as Ordinarius Professor of Theoretical Physics and Director of the Institute of Theoretical Physics.[4][5][6][7]

The formation of the new chair and institute for theoretical physics at Hamburg was a result of advances being made in Germany on atomic physics and quantum mechanics and the personal intervention of Sommerfeld, who helped many of his students get such professorships.[8]

At Hamburg, Lenz trained Ernst Ising and J. Hans D. Jensen; his assistants there included Wolfgang Pauli[9] Pascual Jordan,[10] and Albrecht Unsöld.[11] Together with Pauli and Otto Stern, Lenz built up the Institute into an international center for nuclear physics. They maintained close scientific and personal exchanges with the institutes for theoretical physics at the Universities in Munich (Sommerfeld), Göttingen (Max Born), and Copenhagen (Niels Bohr).[6][7]

When Lenz retired in 1956 he was succeeded by Harry Lehmann.

The Lenz-Ising model[12] can be viewed as the first artificial recurrent neural network (RNN) architecture consisting of neuron-like threshold elements.[13] In 1972, Shun'ichi Amari made this architecture adaptive.[14][13] This learning RNN was popularised in 1982.[15]

Books

Notes

  1. ^ Lenz, W (1920). "Beiträge zum Verständnis der magnetischen Eigenschaften in festen Körpern". Physikalische Zeitschrift. 21: 613–615.
  2. ^ Lenz, W (1924). "Über den Bewegungsverlauf und Quantenzustände der gestörten Keplerbewegung". Zeitschrift für Physik. 24 (1): 197–207. Bibcode:1924ZPhy...24..197L. doi:10.1007/BF01327245. S2CID 121552327.
  3. ^ Lenz – Mathematics Genealogy Project. 1911 Dissertation title: Über das elektromagnetische Wechselfeld der Spulen und deren Wechselstrom-Widerstand, Selbstinduktion und Kapazität.
  4. ^ Mehra, Volume 1, Part 1, p. 334.
  5. ^ Author Catalog: Lenz Archived 2007-02-05 at the Wayback Machine – American Philosophical Society
  6. ^ a b Lenz – ETH Zurich
  7. ^ a b Lenz Biography – Litten
  8. ^ Other examples besides Lenz at Hamburg, include Peter Debye at the University of Zurich, Adolf Kratzer at the University of Münster, and Erwin Fues at the University of Stuttgart, where Sommerfeld’s former student Paul Peter Ewald was already in place. When they were called to other facilities, these personnel effectively became extensions of Sommerfeld’s Institute of Theoretical Physics. See Mehra, Volume 1, Part 1, 1982, p. 335 and Mehra, Volume 5, Part 1, 2001, p. 249.
  9. ^ Pauli began as Hilfsassistent to Lenz at Hamburg on April 1, 1922. He also completed his Habilitation there. Both Lenz and Otto Stern knew of Pauli’s abilities. The mathematician Erich Hecke was dean of the faculty at the time. Hecke waived the normal trail lecture and the colloquium for Habilitation, in recognition of his abilities. The "venia legendi" was conferred on Pauli and he gave his inaugural lecture on February 23, 1924. See Mehra, Volume 1, Part 2, pp. 487 and 672.
  10. ^ In 1923, Jordan went to the University of Göttingen and was instrumental in helping Max Born in founding the matrix mechanics formulation of quantum mechanics in 1925, from a paper by Werner Heisenberg given to Born, in July of that year, for review and publication.
  11. ^ Unsöld was a former doctoral student of Sommerfeld, who got his degree in 1927. See Unsöld – Mathematics Genealogy Project.
  12. ^ Brush, Stephen G. (1967). "History of the Lenz-Ising Model". Reviews of Modern Physics. 39 (4): 883–893. Bibcode:1967RvMP...39..883B. doi:10.1103/RevModPhys.39.883.
  13. ^ a b Schmidhuber, Juergen (2022). "Annotated History of Modern AI and Deep Learning". arXiv:2212.11279 [cs.NE].
  14. ^ Amari, Shun-Ichi (1972). "Learning patterns and pattern sequences by self-organizing nets of threshold elements". IEEE Transactions. C (21): 1197–1206.
  15. ^ Hopfield, J. J. (1982). "Neural networks and physical systems with emergent collective computational abilities". Proceedings of the National Academy of Sciences. 79 (8): 2554–2558. Bibcode:1982PNAS...79.2554H. doi:10.1073/pnas.79.8.2554. PMC 346238. PMID 6953413.

References

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