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J. Low Temp. Physics (1993) 93(5-6) 1059-67.
Creation of Quantized Vortices at the Lambda Transition in Liquid Helium-4
P.C. Hendry, N.S. Lawson, R.A.M. Lee, P.V.E. McClintock and
Department of Physics, Lancaster University, Lancaster, LA1 4YB (UK)
Department of Physics, University of Exeter, Exeter, EX4 4QL (UK).
A fast (approximately 3 ms) adiabatic expansion of a volume of liquid 4He through the lambda transition is being used to study the nature of the transition and to model the cosmological false vacuum to true vacuum phase transition of the early universe. Preliminary results are reported showing that, in accordance with theoretical predictions by W H Zurek [Nature (1985) 317 505] there is copious production of quantized vortex lines, which represent the superfluid analogue of cosmic strings. The line density after the expansion appears to decay in two distinct stages, with a fast decay being followed by a much slower one, in agreement with earlier work on the decay of quantum turbulence created in thermal counterflow. Extrapolation of the initial fast decay suggests an initial line density, immediately following the expansion, of approximately 107 cm-2. Smaller, but still substantial, vortex densities are also found to occur when the system is expanded from below the lambda transition, and the physical implications are discussed.
Keywords: liquid helium, vortices, cosmic strings.