Quantum liquids.

Quantum liquids are systems in which not only the effects of quantum mechanics but also those of the characteristic indistinguishability of elementary particles are important. The most spectacular of these are the systems of bosons (liquid 4He, the Bose alkali gases), which undergo the phenomenon of Bose condensation, and the fermion systems (liquid 3He, the electrons in some metals), which display the related phenomenon of Cooper pairing. I discuss these phenomena and the relation between them.