Effect of Confinement on the Critical Specific Heat of Liquid Helium Near the Lambda Point

Close study is devoted to the order-parameter fluctuations. When the temperature approaches the lambda-point temperature the magnitude of these fluctuations increases, leading to the divergence in the specific heat. When, on the other hand, the liquid helium is confined between parallel solid plates, the growth of the fluctuations is impeded and the divergence in the specific heat is suppressed. By an extension of the epsilon expansion to three-dimensional space we find good agreement between our calculation of the effect of confinement and the data from both earth-based and space experiments.