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Physicist Thouless to give two talks at Lab

One of the world's leading theoretical physicists will present a pair of talks at the Center for Non-Linear Studies (T-CNLS) on Tuesday and Wednesday (April 27-28).

Professor David Thouless of the University of Washington will be continuing his series of Mark Kac Memorial Lectures in the CNLS Conference Room, Building 1690 at Technical Area 3.

Thouless will discuss "Quantized vortices in superfluids and superconductors" at 10 a.m., on Tuesday, and "Dynamics in presence of noise: How special is the Boltzmann distribution?" at 10 a.m., on Wednesday.

"David Thouless is one of the most outstanding condensed matter theorists of his generation. His work on phase transitions, particularly the Kosterlitz-Thouless theory of two-dimensional superfluidity, and his research on quantized vortices in superfluids and superconductors have been highly influential and important contributions to condensed matter physics," Bob Ecke, acting CNLS leader said. "We're honored and at the same time very excited to have him here at the Laboratory for what I know will be two stimulating talks."

Thouless holds a doctorate from Cornell University, where he worked under Hans Bethe, and did postdoctoral work at the University of California, Berkeley, and with Rudolf Peierls at Birmingham University in the United Kingdom.

Thouless' talk on Tuesday will include theoretical reasons and experimental evidence for discrete values (quantized) of circulation around non-superfluid defects in neutral superfluids and in superconductors, including vortices in clusters of trapped atoms. He will discuss some uncertainties and ambiguities in the theory of superfluids that have led to recent questions about how a non-superfluid defect moves, among others.

His talk on Wednesday on dynamics in the presence of noise will provide far-reaching implications for complex systems in general. Many complex systems are plausibly described by a Langevin equation that has two parts: one for motion that can be determined based on initial conditions, and the other a random forcing part that represents noise. Such an equation is descriptive of systems close to thermal equilibrium where the steady state is given by a thermal distribution for which there is no net interchange between any states of the system, Ecke said. Thouless will present an example of a system in which a thermal distribution is obtained without a restriction on net interchange between states of the system.

From 1965 to 1978, Thouless was professor of mathematical physics at Birmingham, where he collaborated with Kosterlitz and worked on electron localization and the spin glass. Since 1980, he has been professor of physics at the University of Washington, where his main interests have been in the Quantum Hall effect, in vortices in superfluids and other problems related to topological quantum numbers.

Thouless is the author of "Quantum Mechanics of Many-Particle Systems and of Topological Quantum Numbers in Nonrelativistic Physics."

He is a Fellow of the Royal Society, Fellow of the American Physical Society, Fellow of the American Academy of Arts and Sciences, and a member of the U.S. National Academy of Sciences. He received the Maxwell Medal and the Paul Dirac Medal from the Institute of Physics (U.K.), the Holweck Medal from the French Physical Society and the Institute of Physics, the Fritz London Award for Low Temperature Physics, the Wolf Prize for Physics, and most recently, the Onsager Prize of the American Physical Society for "the introduction with J. Michael Kosterlitz of the theory of topological phase transitions, as well as fundamental contributions to our understanding of electron localization and the behavior of spin glasses."

Bill Press, Laboratory deputy director for science and technology, is hosting the Kac lectures and Thouless' visit to the Laboratory.

"I strongly support the opportunities presented by distinguished external guest lecturers as David Thouless. I encourage staff members to take advantage of his visit to broaden their scientific interests," Press said.

The Mark Kac Annual Memorial Lecture Series was established in 1985 as a continuing tribute to the founding chairman of the CNLS External Advisory Committee, for his lifelong commitment to the pursuit of scientific research of the highest quality and to the broad dissemination of the results of this research, Ecke said.

Kac, who pioneered the modern development of mathematical probability and its applications to statistical physics, headed the first CNLS External Advisory Committee from 1981 until his death in 1987. At the time, he was at University of Southern California after 20 years each at Cornell, (1940-1961) and at Rockefeller University (1961-1981).

-- Jim Danneskiold

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