Implementation of a Classical Theory for Superfluids: A Recent Study

The superfluidity of helium-4 is still explained by a quantum theory known as the Bose-Einstein condensation. Because it is a system made up of bosons, this theory is quite satisfactory in describing the superfluid state of helium-4 (particles of integer spin). However, the revelation of helium-3 superfluidity in 1971 called this quantum theory into question. In fact, since helium-3 is a system of fermions (particles with a half-integer spin), Bose-Einstein condensation cannot occur in this system. Here, we present a classical (non-quantum) theory of superfluids to address this shortcoming. The transition between fermions and bosons is the same in this new theory. It is based on a fundamental law: "in a superfluid, density is conserved”. In this chapter, we have demonstrated that this simple law accounts for the zero viscosity of superfluids as well as some surprising phenomena that have been observed in the superfluid state, including the liquidity of helium at normal pressure down to 0 K, vaporization without boiling, high thermal conductivity, the fountain effect, the ability to ascend one side of a container wall and descend on the opposite side, and the existence of a critical velocity.