A Model for the Lambda Transition of Helium 4
  Guided by the analogy to the Bose-Einstein condensation of the ideal Bose gas (IBG) we propose a new model for the lambda transition of liquid helium. Deviating from the IBG our model uses phase ordered and localized single-particle functions. This means that finite groups of particles are assumed to be phase-locked. These phase correlations can be related to the singularity at the transition point and to the occurrence of the superfluid density.   The model leads to the following results: 1. A possible explanation of the logarithmic singularity of the specific heat. 2. A characteristic functional form for the superfluid density which yields excellent fits to the experimental data. 3. A quantitative prediction of a small but nonzero entropy content of the superfluid component. 
T. Fliessbach (University of Siegen)