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Abstract |
Thin vortices in fluids and superfluids admit an effective field theory (EFT) description in which they can be
treated as one-dimensional extended objects, or strings. In this theory, vortex lines can interact among
each other as well as with the “bulk” fluid by the exchange of phonons, whose dynamics can be described
by a simple scalar effective theory. The coupling between vortices and sound is however more complicated,
as it requires switching to a magnetic-type dual formulation in which the phonon field is encoded by a
gauge two-form. After a review of the theory and its applications, I will discuss recent work where we show
that the EFT can be recast into the simpler scalar field language, in a description that is valid for closed
string configurations and for bulk modes of wavelength much longer than the typical string size. This is
essentially a systematic expansion of the original EFT in which the string is regarded as a point-like source
with degrees of freedom given by the string’s multipole moments. As an illustration we compute the sound
emitted by an oscillating vortex ring, a calculation that in our field theory language reduces to a simple
Feynman diagram to leading order. |
