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Graduate Student Seminar - 03/09/2012

"Quantized Vortices: Reconnection Fixed Points, Waves and Screamers"

by David Meichle

Friday, March 9, 2012 -- 12:00 p.m.
Large Conference Room, 1207 Energy Research Facility

Advisor:  Professor Daniel Lathrop

Quantized vortices are phase singularities in complex fields. In superfluids, they appear as mobile interacting defects that may cross and reconnect by exchanging tails. Reconnection is a topology-changing event that allows vortex tangles to decay; it is a defining signature of quantum turbulence. This talk will present a basic theoretical background on the Gross-Pitaevskii (GP) model of superfluids, and our recent theoretical and experimental work. A family of complex, stationary solutions of the nonlinear Schrödinger equation (Gross-Pitaevskii equation) that capture quantized vortex reconnections has been found and confirmed numerically, with a robust numerical method for generating well-prepared initial conditions in GP simulations.  Very recent experimental work has confimed that reconnection excites helical Kelvin waves on a quantized vortex, which exhibit self-similarity and are involved in the decay of quantum turbulence.  Preliminary acoustic measurements in 4-He have recorded several perplexing sounds, including "whistlers" going through the Lambda transition, which may have consequences for defect formation theories, relevant in systems with second-order phase transitions such as cosmic strings, superconductors, and liquid crystals.

For additional information about the IREAP Graduate Student Seminars, contact David Meichle.

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