"Vortex Loops and the Superfluid Phase Transition"

Gary A. Williams

UCLA Department of Physics and Astronomy

The role of vortex loops in the superfluid phase transition of liquid helium will be discussed in the talk. After a brief review of the basic properties of liquid helium and of phase transitions, a theory of the superfluid transition using vortex-loop renormalization methods will be outlined. The theory can now be used to calculate many of the thermodynamic properties near the critical temperature, and the predictions of theory are in good agreement with both experiments and recent numerical simulations. Applications of the theory will be discussed for experiments on the 2D to 3D crossover transition of superfluid films adsorbed in porous materials, allowing a measurement of the vortex core size.  Also considered will be the possible role of the loops in the formation of the pseudogap phase in high-Tc superconductors.