Jun 20 – 23, 2022
Max Planck Institut für Festkörperforschung
Europe/Berlin timezone

Fulfillment of sum rules and Ward identities in the multiloop functional renormalization group solution of the Anderson impurity model

Jun 20, 2022, 5:30 PM
2D5 (Max Planck Institut für Festkörperforschung)


Max Planck Institut für Festkörperforschung

Contributed Poster Poster Session


Patrick Chalupa-Gantner (TU Wien)


We showcase several fundamental characteristics of the multiloop functional renormalization group (mfRG) flow by hands of its application to a prototypical many-electron system: the Anderson impurity model (AIM). On the one hand, we analyze the convergence of the algorithm in the different parameter regions of the AIM. On the other hand, by exploiting the converged results, we inspect the fulfillment of (i) sum rules associated to the Pauli principle and (ii) Ward identities related to conservation laws. For the Pauli principle, we observe a systematic improvement by increasing the loop order and including the multiloop corrections to the self-energy. For the Ward identities, we numerically confirm a visible improvement by means of the Katanin substitution. At weak coupling, violations of the Ward identity are further reduced by increasing the loop order in mfRG. For larger interaction values, the overall behavior becomes more complex, and the benefits of the higher-loop terms are mostly present in the contributions at large frequencies.

Primary authors

Patrick Chalupa-Gantner (TU Wien) Mr Fabian B. Kugler (Rutgers University) Ms Cornelia Hille (Universität Tübingen) Mr Jan von Delft (LMU München) Sabine Andergassen (Tuebingen University) Alessandro Toschi (TU Wien)

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