PhD student Nils Krause has developed a reservoir theory of a highly nonlinear reservoir interaction process:

Evaporative damping in open systems theory of Bose-Einstein condensates.

Previously regarded as unimportant (a weak surface term), evaporative damping is shown to be comparable to number damping in regimes of high phase space density. Both processes are weaker than energy damping, which is the dominant reservoir interaction in this regime. At low phase space dentisy - the critical regime - all three reservoir interaction process are important.

The high nonlinearity of evaporative damping poses challenges for analytical and numerical treatments. Our work provides a Wigner phase space derivation of the equations of motion, and some useful analytic bounds and estimates of the physical significance of evaporative damping. We also carry out a dimensional reduction to provide an effective treatment in systems tightly confined along one or two spatial dimensions.

This work completes the first-principles reservoir theory of high-temperature Bose-Einstein condensates.

Congratulations Nils!