Many-body theory of degenerate systems: A simple example
arXiv:cond-mat/0312158
Abstract
The hierarchy of Green functions for (quasi)degenerate systems, presented in cond-mat/0308058, is calculated in detail for the case of a system with closed shells plus a single electron in a two-fold degenerate level. The complete hierarchy is derived explicitly, in terms of Green functions and of Feynman diagrams.
9 pages, 1 figure