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Vortex wake patterns in superfluid4He.
1Department of Physics, University of Virginia, PO Box 400714, Charlottesville, VA 22904-4714, United States of America.
Summary
Quantized vortex rings in superfluid helium-4 create unique wake patterns, distinct from the Landau spectrum. These patterns, resembling Kelvin ship wakes, change with source speed, indicating new elementary excitations.
Area of Science:
- Condensed Matter Physics
- Quantum Fluids
Background:
- Quantized vortex rings exist in superfluid 4He beyond the Landau phonon-roton spectrum.
- These vortex excitations form a separate branch in the elementary excitation spectrum.
Purpose of the Study:
- To investigate the wake patterns generated by uniformly traveling sources in bulk superfluid.
- To connect observed wake patterns to the vortex ring branch of elementary excitations.
Main Methods:
- Theoretical analysis of vortex ring excitation interference.
- Comparison of dispersion laws to gravity waves and Kelvin ship wakes.
Main Results:
- Vortex ring excitations predict wake patterns with elements of the Kelvin ship wake.
- Wake patterns exhibit distinct features (transverse and diverging wavefronts) that vary with source velocity.
- At low speeds, fully developed transverse and diverging wavefronts appear. At intermediate speeds, transverse wavefronts vanish within a cone. At high speeds, only diverging wavefronts confined within a cone are observed.
Conclusions:
- The observed changes in wake patterns serve as experimental indicators for the vortex branch of elementary excitations.
- The dispersion of vortex ring excitations resembles gravity waves with an infrared cutoff.
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