Robert Kraichnan

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Robert Harry Kraichnan (born January 15, 1928 in Philadelphia , † February 26, 2008 in Santa Fe ) was an American theoretical physicist, known for work on the theory of turbulence .

Life

Kraichnan studied at the Massachusetts Institute of Technology (MIT), where he received his doctorate in 1949. In 1949/50 he was assistant to Albert Einstein at the Institute for Advanced Study . He then went to Columbia University and the Courant Institute of Mathematical Sciences of New York University . From 1962 he worked as a freelance consultant and with research grants a. a. for Los Alamos National Laboratory , Princeton University , the Office of Naval Research , Woods Hole Oceanographic Institution, and NASA . As a passionate nature hiker, he lived first in the mountains of New Hampshire and then in New Mexico near Los Alamos and in Santa Fe. Most recently he was "Homewood Professor" in the "Whiting School of Engineering" at Johns Hopkins University since 2003 , but at that time he was already ill.

In 1993 he won the Otto Laporte Prize of the American Physical Society and the Lars Onsager Prize , and in 2003 the Dirac Medal (ICTP) . He has been a member of the National Academy of Sciences since 2000 .

He was married twice and had a son. He last lived in Santa Fe with his wife, the artist and photographer Judy Moore-Kraichnan.

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In the 1950s he also dealt with quantum field theory and the quantum mechanical many-body problem. From 1957 he developed self-consistent field theories, "N-random-coupling-models", in which N copies of a microscopic theory are randomly coupled to one another.

Building on the work of Andrei Kolmogorow (1941), Lars Onsager (1945), Werner Heisenberg (1948), Carl Friedrich von Weizsäcker and others on the statistical theory of turbulence in liquids, from 1957 he developed a field-theoretical formulation in a similar direction to his theory of quantum mechanical many-particle systems ("Direct Interaction Approximation"), to which he gave a Lagrange formulation from 1964/5 (with a correct scaling behavior, which was still incorrectly stated in his work from 1958). The statistical theory of the turbulence of viscous liquids predicts a scale-invariant (that is, following a power law) distribution of the turbulence modes, whereby larger eddies disintegrate into smaller ones and so their energy "dissipates" (dissipation). This is not caused by friction at the molecular level, but by the non-linear effects of the underlying Navier-Stokes equation .

Kraichnan developed his turbulence theories over many decades and was one of the leading American theorists in this field. In 1967 he predicted that in two-dimensional turbulence energy would not only be distributed from large scales (e.g. determined by obstacles in the flow) to smaller ones, such as in three dimensions, but that conversely, smaller fluctuations would increase ("Inverse Energy Cascade"). The two-dimensional theory has applications mainly in oceanography and meteorology. B. confirmed by weather balloon data in the 1980s. A work by Kraichnan from 1994 was also influential, in which he presented an exactly solvable turbulence model (Kraichnan model) and calculated anomalous scaling factors for the passive scalar field occurring in it (which describes advection and e.g. for the concentration of a chemical in a flowing liquid stands).

Kraichnan dealt with general relativity as a schoolboy , won the Westinghouse Science Competition for Schoolchildren and wrote his bachelor thesis on it at MIT in 1947 ("Quantum Theory of the Linear Gravitational Field"). Before Suraj N. Gupta , Richard Feynman and Steven Weinberg he showed at that time that the equations of the general relativity theory follow, under some plausible additional assumptions, from the quantum field theory of a massless spin-2 particle (graviton) corresponding to its linearized form, which is attached to the energy momentum -Tensor of matter couples. The non-linear full equations of the general relativity theory follow from the fact that the contributions of the gravitons themselves are taken into account in the energy-momentum tensor in a self-consistent manner.

Web links

  • Robert H. Kraichnan. In: Physics History Network. American Institute of Physics
  • Jeremy Pearce: Robert Kraichnan, Physicist who studied turbulence, is dead at 80. In: New York Times. March 8, 2008 (English).;
  • Shiyi Chen, Gregory Eyink, Gregory Falkovich, Uriel Frisch, Steven Orszag, Katepalli Sreenivasan: Obituary Robert Harry Kraichnan . In: Physics Today . tape 61 , no. 5 , 2008, p. 70 (English, ictp.it [PDF]).
  • Gregory Eyink, Uriel Frisch: Robert H. Kraichnan . In: Peter A. Davidson (Ed.): A Voyage Through Turbulence . Cambridge University Press, 2011, arxiv : 1011.2383 .

Remarks

  1. ^ Kraichnan Higher Order Interactions in Homogeneous Turbulence Theory , Physics of Fluids, Vol. 1, 1958, p. 358, Irreversible statistical mechanics of incompressible hydromagnetic turbulence , Physical Review, Vol. 109, 1958, pp. 1407-1422, The structure of turbulence at very high Reynolds number , Journal of Fluid Mechanics, Vol. 5, 1959, p. 497
  2. ↑ Kraichnan Decay of isotropic turbulence in the Direct Interaction Approximation , Physics of Fluids Vol. 7, 1964, p. 1030, Kolmogorovs Hypotheses and Eulerian Turbulence Theory , ibid, p. 1723, Lagrangian-history closure approximation for turbulence , Physics of Fluids, Vol. 8, 1965, p. 575, Isotropic Turbulence and inertial range structure , Physics of Fluids, Vol. 9, 1966, p. 1728, Inertial range transfer in 2 and 3 dimensional turbulence , Journal of Fluid Mechanics, Vol. 47, 1971, p. 535
  3. ↑ Kraichnan Inertial Ranges in 2 dimensional turbulence , Physics of Fluids, Vol. 10, 1967, p. 1417
  4. ↑ George Boer, Theodore Shepherd Large-scale two-dimensional turbulence in the atmosphere , Journal Atmospheric Science, Vol. 40, 1983, p. 164
  5. ↑ Kraichnan Anomalous Scaling for a randomly advected passive scalar , Physical Review Letters, Vol. 72, 1994, p. 1016
  6. ^ Preskill, Thorne, foreword in Richard Feynman, "Lectures on Gravitation". They report that even then Einstein was not very enthusiastic about it, since Kraichnan's approach bypassed Einstein's own hard-won path through the geometric interpretation of his field equations. Preskill and Thorne also compare the various works of Gupta, Feynman, Kraichnan, Deser, Wald, Weinberg: ps file
  7. ↑ Kraichnan "Special-Relativistic Derivation of Generally Covariant Gravitation Theory", Physical Review, Vol. 98, 1955, pp. 1118-1122. "Possibility of unequal gravitational and inertial masses", Physical Review, Vol. 101, 1956, pp. 482-488
personal data
SURNAME Kraichnan, Robert
ALTERNATIVE NAMES Kraichnan, Robert Harry (full name)
BRIEF DESCRIPTION American physicist
DATE OF BIRTH January 15, 1928
PLACE OF BIRTH Philadelphia
DATE OF DEATH February 26, 2008
Place of death Santa Fe