The phase transition of liquid He-4 into the superfluid state has been studied intensively over many decades. We investigate this lambda-transition in the framework of the Almost Ideal Bose Gas Model (AIBG). The AIBG is introduced in the paper

A Model for the Lambda-Transition of Helium pdf-file (282 kB)

The model is quite different from other competing approaches and leads to novel explanations and predictions.

A central prediction of the AIBG is that of a non-vanishing superfluid entropy. The papers (coauthor R. Schaefer)

The Two-Fluid Model with Superfluid Entropy pdf-file (194 kB)

A new sound mode in liquid Helium 4? pdf-file (107 kB)

investigate the consequences of this prediction, and propose an experiment for measuring the suprafluid entropy content.

Spatial correlations of the helium liquid have been calculated by R. Blendowske:

Microscopic calculation of the temperature anomaly of spatial correlations in liquid He-4 (pdf, 153 kB)Further papers in the framework of the AIBG are:

Asymptotic temperature dependence of the superfluid density in liquid He-4 pdf-file (273 kB)

Phase ordering at the lambda transition in liquid Helium 4 pdf-file (238 kB)

Effective Ginzburg-Landau model for superfluid Helium 4 pdf-file (220 kB)

The basis of these investigations is the work on the microscopic treatment of alpha decay by Fliessbach. For describing the alpha decay, one has to calculate the probability with which the structure "alpha-particle plus daughter nucleus" is preformed in the parent nucleus. Up to the 1970s the effects of the antisymmetrization (between the alpha-particle and the daughter nucleus, exit channel) have not been taken into account properly in the corresponding calculations. The correct antisymmetrization and normalization in the exit channel leads to propabilities that exceed the previously calculated preformation probabilities by factors of the order 100 (for the lead region). This implies that the nuclear shell model is quite able to reproduce the absolute alpha decay rates.

This approach has been extended to the exotic decays of atomic nuclei. We calculated, for example, the C-14-decay of radium. An overview of this work (coauthors R. Blendowske and H. Walliser) is presented in

Many-Body Approach to Alpha and Cluster Radioactivity (pdf, 69 kB)

published in "Nuclear Decay Modes" ed. by D. N. Poenaru, IOP Publishing Ltd 1996.

This work presents a simplified introduction into the underlying microscopic theory and tables with predictions for numerous exotic decays. References to original papers may be found in this article, too.