Michał
Śliwiński
Warsaw University of Technology
The Kelvin–Helmholtz instability (KHI) in superfluid systems with annular geometry has recently attracted significant attention. While numerical studies based on Gross–Pitaevskii and Zaremba–Nikuni–Griffin models have explained some of its dynamics, they still predict the instability's growth rates incorrectly. We employ the SLDA framework to simulate KHI in annular superfluid systems across interaction regimes for temperatures T/Tc ≈ 0.0 and 0.33, and compare the resulting dynamics and KHI growth rates with existing theoretical models and experimental observations. We do not observe sensitivity of the instability growth rate to the interaction regime (BCS vs UFG), in contrast to experimental findings. This discrepancy persists even when finite-temperature effects are included. Additionally, systematic deviations from the Point-Vortex Model are identified for modes with m/Δw ∈ (0.6, 0.8), for which no clear mechanism has been established. In the deep BCS regime, the dynamics change qualitatively: vortex proliferation at the inner edge of the ring dominates, operating on shorter timescales than KHI and suppressing its development. Our results indicate limitations of the SLDA in capturing experimentally observed interaction-dependent growth rates and reveal a competing instability mechanism in the BCS regime. These findings highlight unresolved aspects of vortex dynamics in annular superfluids and motivate further theoretical investigation.
Location: seminar room D, Al. Lotników 32/46, also available via Zoom under
https://us06web.zoom.us/j/87057373249?pwd=MNnyk4rUf9cOVZoxeqIaKkhwYk5STm.1
