Navegando por Autor "Kopietz, Peter"
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Artigo Ward identities for the Anderson impurity model: derivation via functional methods and the exact renormalization group(IOP Publishing, 2010-08-27) Ferraz Filho, Álvaro; Kopietz, Peter; Bartosch, Lorenz; Costa, Lúcio; Isidori, AldoUsing functional methods and the exact renormalization group we derive Ward identities for the Anderson impurity model. In particular, we present a nonperturbative proof of the Yamada–Yosida identities relating certain coefficients in the low-energy expansion of the self-energy to the thermodynamic particle number and spin susceptibilities of the impurity. Our proof underlines the relation of the Yamada–Yosida identities to the U(1) × U(1) symmetry associated with the particle number and spin conservation in a magnetic field. PACS numbers: 72.15.Qm, 71.27.+q, 71.10.Pm