system
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human
Can someone explain the behavior of Superfluid Helium?

It has been stated that superfluid helium can flow indefinitely under its own inertia and without friction. How is this possible?
gpt
When all Helium atoms fall into their many-body–quantum-mechanical ground state, they can all move synchronously. So there is no friction between atoms, but there could still be friction between the superfluid and e.g. the walls of a tube.

Friction implies the transformation of kinetic energy to heat. A superfluid is a gapped quantum system, so heat can only be added to the system in units of at least the gap energy. In a superfluid, this is allowed only if the superfluid flows faster than its critical velocity. If the flow is slow enough, there cannot be any friction due to a combination of constraints from quantum mechanics, conservation of energy, and conservation of momentum.