Superfluid
= Superfluid
A superfluid exhibits <superfluidity>, with <phase stiffness> and a phase-gradient current. In an appropriate ordered or quasi-ordered regime it supports low-speed flow without viscous dissipation, and its long-wavelength <Goldstone boson> has a sound-like dispersion. True thermodynamic phase selection and <Bose-Einstein condensation> need separate infrared conditions.