  We propose and explore a new finite temperature phase of translationally
invariant multi-component liquids which we call a "Quantum Disentangled Liquid"
(QDL) phase. We contemplate the possibility that in fluids consisting of two
(or more) species of indistinguishable quantum particles with a large mass
ratio, the light particles might "localize" on the heavy particles. We give a
precise, formal definition of this Quantum Disentangled Liquid phase in terms
of the finite energy density many-particle wavefunctions. While the heavy
particles are fully thermalized, for a typical fixed configuration of the heavy
particles, the entanglement entropy of the light particles satisfies an area
law; this implies that the light particles have not thermalized. Thus, in a QDL
phase, thermal equilibration is incomplete, and the canonical assumptions of
statistical mechanics are not fully operative. We explore the possibility of
QDL in water, with the light proton degrees of freedom becoming "localized" on
the oxygen ions. We do not presently know whether a local, generic Hamiltonian
can have eigenstates of the QDL form, and if it can not, then the non-thermal
behavior discussed here will exist as an interesting crossover phenomena at
time scales that diverge as the ratio of the mass of the heavy to the light
species also diverges.
