Bose-Einstein condensation of two interacting particles
  We investigate the notion of Bose-Einstein condensation of interacting particles. The definition of the condensate is based on the existence of the dominant eigenvalue of the single-particle density matrix. The statistical properties and the characteristic temperature are computed exactly in the soluble models of two interacting atoms. 
M. A. Cirone, K. Goral, K. Rzazewski, M. Wilkens