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Diagrammatic method for investigating universal behavior of impurity systems

Kurt Fischer
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Abstract

The universal behavior of magnetic impurities in a metal is proved with the help of skeleton diagrams. The energy scales are derived from the structure of the skeleton diagrams. A minimal set of skeleton diagrams is sorted out that scales exactly. For example, the non-crossing approximation for the Anderson impurity model can describe the crossover phenomenon. The universal Wilson-number is calculated within the non-crossing approximation. The method allows for an assessment of various approximations for impurity Hamiltonians.

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Kurt Fischer. 1998-07-09. Diagrammatic method for investigating universal behavior of impurity systems. https://doi.org/10.1103/physrevb.55.13575

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