Phase ordering at the lambda transition in liquid 4-He
  A modified ideal Bose gas model is proposed as an approach for liquid helium at the lambda point. The decisive modification of the ideal Bose gas model is the use of phase ordered single particle functions. The entropy due to this phase ordering is calculated. Its statistical expectation value yields a logarithmic singularity of the specific heat. 
Torsten Fliessbach (University of Siegen, Germany)