Existence and absence of Bose-Einstein condensation in the interacting random Kac-Luttinger model

In this paper, we study interacting bosons at zero temperature in a random and higher-dimensional continuum model introduced by Kac and Luttinger.

For weak interactions we prove that there is condensation in the lowest eigenstate of the one-particle Hamiltonian (type-I BEC).

For strong interactions, however, we show that condensation in a localized state cannot occur.

We also prove generalized condensation, where a family of eigenstates of the one-particle Hamiltonian is macroscopically occupied as a whole.

Combining these results yields a scenario where there is generalized condensation into a family of eigenstates of the one-particle Hamiltonian, but none of them is macroscopically occupied itself (type-III BEC).

This proves a transition in the type of condensation.

To the best of our knowledge, this is the first rigorous result in this direction for a random continuum model in higher dimensions.