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Many-body theory of degenerate systems

Christian Brouder
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Abstract

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 determinant. The double-source (or closed-time-path) formalism of nonequilibrium quantum field theory is used to derive an expression for the average value of a product of interacting fields when the initial state is not the vacuum or a Slater determinant. Quantum group techniques are applied to derive the hierarchy of unconnected Green functions and the hierarchy of connected ones.

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Christian Brouder. 2003-12-09. Many-body theory of degenerate systems. https://arxiv.org/abs/cond-mat/0309558

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