General Colloquium
January 25 - 4:00pm Phys 223
(Coffee at 3:30p.m. in room 242)

David Ceperley
Professor of Physics
University of Illinois at Champaign-Urbana.

Title: "The Path Integral Theory of Superfluidity and Bose Condensation."

Abstract:
Feynman(1953) introduced imaginary-time path integrals to understand superfluid 4He. Path integrals are an exact "isomorphism" between quantum systems and the classical statistical mechanics of ring "polymers." Bose symmetry of the wave function implies that the polymers are allowed to "cross-link'' or exchange. The specific heat singularity is a consequence of this cross-linking, momentum condensation is related to the end-to-end distribution of a single open-ended polymer: if the ends become delocalized, the quantum system is bose condensed. Superfluidity (coupling to the boundaries) is proportional to the mean squared flux of polymers through a surface. We have developed specialized simulation methods (Path Integral Monte Carlo) based on the Metropolis Monte Carlo method, to simulate boson systems.

Recent applications are to molecular hydrogen on surfaces, superfluidity in small helium droplets and bose-condensation in dilute atomic gases.

Brief Bio:
David Ceperley was an original developer of the variational, Green's Function and Path Integral Monte Carlo method for fermion and boson systems. For this work he was awarded the 1994 Feenberg Medal and the 1997 Rahman Prize for Computational Physics by the American Physical Society. He has worked extensively on various types of supercomputers over the last eighteen years and has been an NCSA staff member the last ten years.

Department of Physics and NCSA, University of Illinois 1110 West Green St., Urbana, IL, 61801 Phone: (217) 244-0646; Fax: (217) 244-2909; e-mail: ceperley@uiuc.edu Web Site: www.ncsa.uiuc.edu/Apps/CMP/ceperley.html

Education:
University of Michigan, B.S. Physics, Mathematics, 1967-71.
Cornell University, Ph.D. Physics, 1971-76.
Lab. de Physique Theorique, Orsay, France, Postdoctoral fellowship, 1976-77.
Rutgers University, Postdoctoral fellowship, 1977-78.

Employment:
1991- Professor of Physics, University of Illinois at Champaign-Urbana.
1997-98 Associate Director of Applications, Nat. Center for Supercomputing Applications.
1987-91 Associate Professor of Physics, University of Illinois.
1987- Research Scientist, National Center for Supercomputing Applications.
1981-87 Staff Scientist, Lawrence Livermore Nat. Lab.
1978-81 Staff Scientist, Nat. Resource for Computation in Chemistry, Lawrence Berkeley Lab.