My e-mail address is email@example.com and my phone number is (206)685-2393; my office number is PAB B423.
I worked on the theory of nuclear matter with Hans Bethe for my PhD, and was a post-doc with Rudolf Peierls in Birmingham, England, where I wrote a book on The Quantum Mechanics of Many-Particle Systems. I was a professor at Birmingham from 1965 to 1978, and have been at the University of Washington since 1980. I retired in 2003, and am now Emeritus Professor. I am a Fellow of the Royal Society and of the American Physical Society, and a Member of the National Academy of Sciences. My best known work, on phase transitions in two dimensions driven by defect unbinding, was done with Michael Kosterlitz in the early seventies. For this work we were awarded the Lars Onsager Prize of the American Physical Society for the year 2000.
Currently my interests of are centered around the topic of topological quantum numbers; the grant from NSF supporting our work (NSF award DMR-0201948) has this title, and I have written a book called Topological Quantum Numbers in Nonrelativistic Physics which was published by World Scientific in February 1998. The book contains my own text as well as a collection of reprints of classic papers on the subject. Under this heading there are three main current lines of work, on the dynamics of quantized vortices in superfluids, on the quantum Hall effect, and on Bose condensation in dilute gases.
Some recent members of the group were Sung Wu Rhee, who took his PhD in 2003, and is now Research Assistant Professor at the University of Arkansas Medical Center, Jens Koch, a visitng student from Berlin, who is now a post-doc at Yale, Chulan Kwon, who was on sabbatical from Myungji University in Korea, and one Affiliate Associate Professor, Ping Ao. <\p>
Topological quantum numbers are quantum numbers that are determined by the topology of the system, rather than by its symmetry, as are the more familiar quantum numbers such as angular momentum. Unlike the symmetry-dependent quantum numbers, topological quantum numbers are insensitive to perturbations, and some of them have been shown to be quantized with extraordinarily high precision. The circulation in superfluid helium, the magnetic flux in a superconducting loop, and the Hall conductance in a quantum Hall device are examples of topological quantum numbers. The last two can be measured very accurately, and their quantization serves as the basis for the best secondary standards of voltage and of electrical resistance. There are other topological quantum numbers that have only a finite number of possible integer values, and these, while useful for classifying possible states of the system, do not lead to the possibility of high precision in measurement.
Quantized vortices in superfluid helium, around which the circulation is equal to h/m, where m is the mass of the helium atom, have been known both theoretically and experimentally, for many years, but there still seems to be controversy about their dynamics, both the forces acting on them and their effective masses. The corresponding questions about the dynamics of a flux line in a superconductor seem to be even more controversial. We think that we have provided clear and unambiguous answers to some of these questions in the situation in which there is no background disorder. This topic was the subject of Carlos Wexler's PhD dissertation, and Jian-Ming Tang is continuing work on it. In recent work with Michael Geller (Georgia) and Joe Vinen (Birmingham) we have been successfully exploring these controversies using two-fluid hydrodynamics. A preprint of this work can be found here.