421 citations · 1.5k across the 60 of their papers we have counts for
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Many-body theory of degenerate systems: A simple example
Christian Brouder
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 ele…
Quantum field theory and Hopf algebra cohomology
Christian Brouder, Bertfried Fauser, Alessandra Frabetti +1
We exhibit a Hopf superalgebra structure of the algebra of field operators of quantum field theory (QFT) with the normal product. Based on this we construct the operator product an…
Many-body theory of degenerate systems
Christian Brouder
The many-body theory of degenerate systems is described in detail. More generally, this theory applies to systems with an initial state that cannot be described by a single Slater…
A many-body approach to crystal field theory
Christian Brouder
A self-consistent many-body approach is proposed to build a first-principles crystal field theory, where crystal field parameters are calculated ab initio. Many-body theory is used…
Quantum field theory of degenerate systems
Christian Brouder
To set up a self-consistent quantum field theory of degenerate systems, the unperturbed state should be described by a density matrix instead of a pure state. This increases the co…