J. Stein: Flow equations and the Ruderman-Kittel-Kasuya-Yosida interaction, Eur. Phys. J. B 12 (1999) 5 (Postscript-File)
The method of continuous unitary transformations is applied to obtain the indirect exchange coupling between local magnetic moments in an electron gas. The derivation of the exact analytical expression for the resulting Ruderman-Kittel-Kasuya-Yosida interaction is presented for general dimensionality. In odd dimensions, the result can be shown explicitly to exhibit universal 2kF oscillatory behaviour on all length scales.