Robert Kraichnan
Robert H. 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. 1949/50, he was at the Institute for Advanced Study, assistant to Albert Einstein. After that, he was at Columbia University and the Courant Institute of Mathematical Sciences of New York University. From 1962 he worked as a freelance consultant and research fellowships and for the Los Alamos National Laboratory, Princeton University, the Office of Naval Research, the Woods Hole Oceanographic Institution and NASA. He lived as a passionate nature walkers first in the mountains of New Hampshire and then in New Mexico near Los Alamos and Santa Fe. He was most recently since 2003 " Homewood Professor " in the " Whiting School of Engineering" at the Johns Hopkins University, at that time, already ill.
In 1993 he won the Otto Laporte Award of the American Physical Society and the Lars Onsager - Price, 2003, the Dirac Medal ( ICTP ). He was a member of the National Academy of Sciences since 2000.
He was married twice and had a son. He last lived with his wife, the artist and photographer Judy Moore - Kraichnan, in Santa Fe.
Work
In the 1950s, he was also involved in quantum field theory and the quantum mechanical many-body problem. He developed it from 1957 self-consistent field theories, "N -random- coupling - models", in which N copies of a microscopic theory are coupled to each other in a random manner.
Building on the work of Andrei Kolmogorov (1941 ), Lars Onsager (1945 ), Werner Heisenberg ( 1948), Carl Friedrich von Weizsäcker and others on the statistical theory of turbulence of fluids he developed from 1957 onwards a field theoretical formulation in a similar direction as his theory of quantum-mechanical many-body systems ( "Direct interaction approximation " ), to which he gave a Lagrangian formulation in 1964 /5 ( with a correct scaling behavior that was reported incorrectly in his work of 1958). The statistical theory of turbulence viscous liquids predicts a scale-invariant (ie, following a power law ) requires distribution of turbulence modes, with larger vortices break down into smaller and so their energy " melts " (dissipation ). Which is not caused by friction at a molecular level but by the nonlinear effects of the underlying Navier-Stokes equation.
Kraichnan turbulence developed his theories over many decades and was one of the leading American theorist in this field. In 1967, he predicted that in the two-dimensional turbulence energy not only from large scales ( approximately determined by obstacles in the flow stream ) distributed to smaller ones like in three dimensions, but that, conversely, smaller fluctuations grow ( "Inverse Energy Cascade" ). The two-dimensional theory has applications especially in oceanography and meteorology, and was, for example, confirmed in the 1980s by weather balloon data. Influential was also a work Kraichnans 1994, in which he presented an exactly solvable turbulence model ( Kraichnan model) and anomalous scaling factors for the occurring therein passive scalar field calculated ( the advection describes and for example for the concentration of a chemical in a flowing liquid is ) ..
Kraichnan already dealt as a student with general relativity, thus won the Westinghouse Science Competition for students and wrote his thesis at MIT in 1947 ( " Quantum Theory of the Gravitational Field Linear "). Before Suraj N. Gupta, Richard Feynman and Steven Weinberg, he showed then that the equations of general relativity under some plausible additional assumptions follow from the corresponding their linearized form quantum field theory of a massless spin -2 particle ( graviton ) applied to the energy-momentum tensor of matter coupled .. the nonlinear full equations of general relativity follow from the fact that in the energy -momentum tensor in a self-consistent manner the contributions of gravitons even be considered.