  In a recent article, Yefsah et al. [Nature 499, 426 (2013)] report the
observation of an unusual excitation in an elongated harmonically trapped
unitary Fermi gas. After phase imprinting a domain wall, they observe
oscillations almost an order of magnitude slower than predicted by any theory
of domain walls which they interpret as a "heavy soliton" of inertial mass some
200 times larger than the free fermion mass or 50 times larger than expected
for a domain wall. We present compelling evidence that this "soliton" is
instead a quantized vortex ring by showing that the main aspects of the
experiment can be naturally explained within the framework of time-dependent
superfluid DFT.

Quantum Gases