Toichiro Kinoshita

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Toichiro Kinoshita
Toichiro Kinoshita, physicist.jpg
Born
木下東一郎, Kinoshita Tōichirō

(1925-01-23)January 23, 1925
DiedMarch 23, 2023(2023-03-23) (aged 98)
OccupationTheoretical physicist
Known for Kinoshita–Lee–Nauenberg theorem
Awards Sakurai prize (1990)
Guggenheim Fellowship (1973)
Academic background
Education University of Tokyo
Doctoral advisor Sin-Itiro Tomonaga

Tōichirō Kinoshita (木下東一郎, Kinoshita Tōichirō ; January 23, 1925 – March 23, 2023) was a Japanese-born American theoretical physicist.

Contents

Kinoshita was born in Tokyo on January 23, 1925. He studied physics at the University of Tokyo, earning his bachelor's degree in 1947 and then his PhD in 1952. Afterwards he spent two years as a postdoctoral researcher of the Institute of Advanced Study, Princeton, New Jersey, and then one year at Columbia University. His research interests included quantum field theory, and the Standard Model. [1]

Kinoshita worked at the Newman Laboratory of Nuclear Studies at Cornell University from 1955. He was at first a research associate. In 1958 he became assistant professor, and in 1960 associate professor. He became a full professor in 1963, and in 1992 he was appointed Goldwin Smith professor. In 1995 he retired from Cornell as professor emeritus. In 1962–63 he was a Ford Fellow at CERN. He was a guest professor at the University of Tokyo, at CERN, at the national laboratory for high-energy physics KEK in Japan, and at RIKEN in Japan. [1] [2]

Kinoshita was known for his extensive and detailed calculations of quantum electrodynamics (QED), the theory of the interaction of light and matter, on which physicist Abraham Pais called him the "expert among experts". [3] QED is often described as the most accurate physical theory in existence. Among the best-known examples are Kinoshita's calculations of the anomalous magnetic moments of the electron and the muon.

Research

Kinoshita worked on a range of topics in QED. While at the Institute for Advanced Study he calculated to high precision the ground state energy of Helium. [4] At Cornell, Kinoshita collaborated with Alberto Sirlin to calculate the radiative corrections to parity-nonconserving muon decay and β decay. [5] He collaborated with Richard Feynman to calculate the radiative correction to the ratio of decay rates for a pion decaying to an electron over that for decaying to a muon, notated as Γ(π → eν)/Γ(π → μν). [6] In 1962 he showed that Feynman amplitudes in quantum electrodynamics remain finite in the limit of propagator masses vanishing, i.e., all infrared divergences cancel. [7] This became known as the Kinoshita-Lee-Nauenberg theorem. In the 1970s he worked on quantum chromodynamics and quarkonium - spectroscopy with Estia Eichten, Kenneth Lane, Kurt Gottfried, and Tung-Mow Yan.

Kinoshita is best known for his calculations of the anomalous magnetic moments of the electron and muon. According to the Dirac theory, [8] the magnetic moment of the electron should equal two. However, interactions of the electron with a magnetic field will deviate this value from two; the difference is referred to as the anomalous magnetic moment or simply “the anomaly” ɑe. The value of ɑe can be calculated as a perturbative expansion in powers of α/π, where α = e2/(4πεoħc) ≈ 1/137 is the fine structure constant. The lowest-order (“second-order”) term was calculated by Julian Schwinger, [9] and the next (fourth-order) term was calculated by Karplus and Kroll [10] (with a sign error subsequently corrected [11] ). The fourth-order term is obtained by evaluating seven distinct amplitudes or "Feynman diagrams." These calculations were all performed analytically, and their accuracy was limited only by the value of α, which cannot be calculated from first principles and must be measured by experiment.

The sixth-order term consists of 72 Feynman diagrams, and Kinoshita evaluated these to high precision numerically using computers. [12] He revised this calculation in 1995 [13] using faster computers and higher precision computational techniques. Working with his students, he subsequently calculated the eighth-order terms (891 Feynman diagrams) [14] and, with great effort over several years, the tenth-order terms (12672 Feynman diagrams). [15]

In 2001, Kinoshita and a group in Marseille found a sign difference in their respective calculations of the π0 pole contribution to the sixth-order light-by-light amplitude. [16] Kinoshita and his student M. Hayakawa ultimately traced this to an incorrect implementation of the antisymmetric Levi-Civita tensor εαβγδ used in the computation code "Form" [17] that had been used. [18] It took a while to fix this software bug by the developers. [19]

Personal life and death

Kinoshita married Masako Matsuoka in 1951. He and his wife has three daughters. His wife died in 2022. [20]

Kinoshita died at his home in Amherst, Massachusetts, on March 23, 2023, at the age of 98. [21] He was survived by daughters and sons-in-law Kay and Alan Schwartz, June and Tod Machover, and Ray and Charles C. Mann, three sisters in Japan, and six grandchildren. [22]

Honors and awards

In 1962–63 he was a Ford Foundation Fellow at CERN. In 1973–74 he was a Guggenheim Fellow. He was awarded the Sakurai Prize from the American Physical Society in 1990; the SUN-AMCO Medal from the International Union of Pure and Applied Science in 1998; the Gian Carlo Wick Gold Medal in 2010; and the Toray Science and Technology Prize in 2019. He was elected to the National Academy of Sciences in 1991. [1]

Books

Related Research Articles

<span class="mw-page-title-main">Quantum electrodynamics</span> Quantum field theory of electromagnetism

In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons and represents the quantum counterpart of classical electromagnetism giving a complete account of matter and light interaction.

<span class="mw-page-title-main">Positronium</span> Bound state of an electron and positron

Positronium (Ps) is a system consisting of an electron and its anti-particle, a positron, bound together into an exotic atom, specifically an onium. Unlike hydrogen, the system has no protons. The system is unstable: the two particles annihilate each other to predominantly produce two or three gamma-rays, depending on the relative spin states. The energy levels of the two particles are similar to that of the hydrogen atom. However, because of the reduced mass, the frequencies of the spectral lines are less than half of those for the corresponding hydrogen lines.

<span class="mw-page-title-main">Fine-structure constant</span> Dimensionless number that quantifies the strength of the electromagnetic interaction

In physics, the fine-structure constant, also known as the Sommerfeld constant, commonly denoted by α, is a fundamental physical constant which quantifies the strength of the electromagnetic interaction between elementary charged particles.

<span class="mw-page-title-main">Julian Schwinger</span> American theoretical physicist (1918–1994)

Julian Seymour Schwinger was a Nobel Prize-winning American theoretical physicist. He is best known for his work on quantum electrodynamics (QED), in particular for developing a relativistically invariant perturbation theory, and for renormalizing QED to one loop order. Schwinger was a physics professor at several universities.

<span class="mw-page-title-main">Shin'ichirō Tomonaga</span> Japanese physicist (1906-1979)

Shinichiro Tomonaga, usually cited as Sin-Itiro Tomonaga in English, was a Japanese physicist, influential in the development of quantum electrodynamics, work for which he was jointly awarded the Nobel Prize in Physics in 1965 along with Richard Feynman and Julian Schwinger.

<span class="mw-page-title-main">Renormalization</span> Method in physics used to deal with infinities

Renormalization is a collection of techniques in quantum field theory, statistical field theory, and the theory of self-similar geometric structures, that are used to treat infinities arising in calculated quantities by altering values of these quantities to compensate for effects of their self-interactions. But even if no infinities arose in loop diagrams in quantum field theory, it could be shown that it would be necessary to renormalize the mass and fields appearing in the original Lagrangian.

In theoretical physics, a chiral anomaly is the anomalous nonconservation of a chiral current. In everyday terms, it is equivalent to a sealed box that contained equal numbers of left and right-handed bolts, but when opened was found to have more left than right, or vice versa.

In quantum field theory, and specifically quantum electrodynamics, vacuum polarization describes a process in which a background electromagnetic field produces virtual electron–positron pairs that change the distribution of charges and currents that generated the original electromagnetic field. It is also sometimes referred to as the self-energy of the gauge boson (photon).

<span class="mw-page-title-main">History of quantum field theory</span>

In particle physics, the history of quantum field theory starts with its creation by Paul Dirac, when he attempted to quantize the electromagnetic field in the late 1920s. Major advances in the theory were made in the 1940s and 1950s, leading to the introduction of renormalized quantum electrodynamics (QED). The field theory behind QED was so accurate and successful in predictions that efforts were made to apply the same basic concepts for the other forces of nature. Beginning in 1954, the parallel was found by way of gauge theory, leading by the late 1970s, to quantum field models of strong nuclear force and weak nuclear force, united in the modern Standard Model of particle physics.

In quantum electrodynamics, the anomalous magnetic moment of a particle is a contribution of effects of quantum mechanics, expressed by Feynman diagrams with loops, to the magnetic moment of that particle. The magnetic moment, also called magnetic dipole moment, is a measure of the strength of a magnetic source.

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<span class="mw-page-title-main">Schwinger effect</span> Decay of strong electromagnetic fields into particles

The Schwinger effect is a predicted physical phenomenon whereby matter is created by a strong electric field. It is also referred to as the Sauter–Schwinger effect, Schwinger mechanism, or Schwinger pair production. It is a prediction of quantum electrodynamics (QED) in which electron–positron pairs are spontaneously created in the presence of an electric field, thereby causing the decay of the electric field. The effect was originally proposed by Fritz Sauter in 1931 and further important work was carried out by Werner Heisenberg and Hans Heinrich Euler in 1936, though it was not until 1951 that Julian Schwinger gave a complete theoretical description.

A g-factor is a dimensionless quantity that characterizes the magnetic moment and angular momentum of an atom, a particle or the nucleus. It is essentially a proportionality constant that relates the different observed magnetic moments μ of a particle to their angular momentum quantum numbers and a unit of magnetic moment, usually the Bohr magneton or nuclear magneton. Its value is proportional to the gyromagnetic ratio.

Quantum electrodynamics (QED), a relativistic quantum field theory of electrodynamics, is among the most stringently tested theories in physics. The most precise and specific tests of QED consist of measurements of the electromagnetic fine-structure constant, α, in various physical systems. Checking the consistency of such measurements tests the theory.

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<span class="mw-page-title-main">Schwinger limit</span> Energy scale at which vacuum effects become important

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Norman Myles Kroll was an American theoretical physicist, known for his pioneering work in QED.

Alberto Sirlin was an Argentine theoretical physicist, specializing in particle physics.

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References

  1. 1 2 3 T. Kinoshita. History. American Institute of Physics (AIP). Accessed October 4, 2018.
  2. "Toichiro Kinoshita, Department of Physics". Cornell University (physics.cornell.edu).
  3. Pais, A.1986. Inward Bound: Of Matter and Forces in the Physical World. Oxford: Oxford University Press, p. 466.
  4. T. Kinoshita, Phys. Rev. 105, 1490 (1957).
  5. T. Kinoshita and A. Sirlin, Phys. Rev. 113, 1652 (1959); T. Kinoshita and A. Sirlin, Phys. Rev. 107, 593 (1957).
  6. T. Kinoshita, Phys. Rev. Lett. 2, 477 (1959).
  7. T. Kinoshita, Jour. Math. Phys. 3, 650 (1962).
  8. P. A. M. Dirac, Proc. Roy. Soc. Lond. A 117, 610 (1928).
  9. J. S. Schwinger, Phys. Rev. 73, 416 (1948); J. Schwinger, Phys. Rev. 75, 898 (1949).
  10. R. Karplus and N. M. Kroll, Phys. Rev. 77, 536 (1950)
  11. A. Petermann, Helv. Phys. Acta 30, 407 (1957); C. M. Sommerfield, Phys. Rev. 107, 328 (1957).
  12. P. Cvitanovic and T. Kinoshita, Phys. Rev. D 10, 4007 (1974).
  13. T. Kinoshita, Phys. Rev. Lett. 75, 4728 (1995).
  14. T. Kinoshita and M. Nio, Phys. Rev. D 73, 013003 (2006), hep-ph/0507249; T. Aoyama, M. Hayakawa, T. Kinoshita, and M. Nio, Nucl. Phys. B 740, 138 (2006), hep-ph/0512288.
  15. T. Aoyama, M. Hayakawa, T. Kinoshita, and M. Nio, Phys. Rev. Lett. 109, 111808 (2012), arXiv:1205.5370; T. Aoyama, M. Hayakawa, T. Kinoshita, and M. Nio, Phys. Rev. D 91, 033006 (2015) [Erratum: Phys.Rev.D 96, 019901 (2017)], arXiv:1412.8284; T. Aoyama, T. Kinoshita, and M. Nio, Phys. Rev. D 97, 036001 (2018), arXiv:1712.06060; T. Aoyama, T. Kinoshita, and M. Nio, Atoms 7, 28 (2019).
  16. M. Hayakawa and T. Kinoshita, Phys. Rev. D 57, 465 (1998) [Erratum: Phys.Rev.D 66, 019902 (2002)], hep-ph/9708227.
  17. J. A. M. Vermaseren (2000), math-ph/0010025.
  18. M. Hayakawa and T. Kinoshita (2001), hep-ph/0112102.
  19. Schwartzschild, 2002
  20. https://ithacavoice.org/2022/08/obituary-masako-kinoshita/
  21. "物理学者の木下東一郎・米コーネル大名誉教授が死去、98歳…「最も高精度の理論計算値」" (in Japanese). Yomiuri Shimbun. 29 March 2023. Retrieved 29 March 2023.
  22. https://www.ithacajournal.com/obituaries/bps138832