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TT 33.7: Vortrag
Mittwoch, 18. März 2020, 11:15–11:30, HSZ 201
Symmetric improved estimators for continuous-time quantum Monte Carlo — •Josef Kaufmann1, Patrik Gunacker1, Alexander Kowalski2, Markus Wallerberger1, Giorgio Sangiovanni2, and Karsten Held1 — 1Institut für Festkörperphysik, TU Wien — 2Institut für Theoretische Physik und Astrophysik, Universität Würzburg
Continuous-time quantum Monte Carlo in the hybridization expansion is the current method of choice for solving the multiorbital Anderson impurity model. However, the results suffer from notoriously high noise at large Matsubara frequencies. Previously, this problem has been addressed e.g. by improved estimators 
We now go beyond this by deriving equations of motion for Green’s functions symmetrically with respect to all time arguments. The resulting equations relate the one- and two-particle Green’s function to correlators of up to six particles at four times , which can be computed by worm sampling [3, 4]. Finally, we arrive at self-energies and vertex functions that are practically noiseless at all frequencies.
This increase in precision leads to improved convergence behavior in dynamical mean-field theory calculations, as well as more reliable analytical continuation to real frequencies.
 H. Hafermann et al., PRB 85, 205106 (2012)
 J. Kaufmann, P. Gunacker et al., PRB 100, 075119 (2019)
 P. Gunacker et al., PRB 92, 155102 (2015)
 M. Wallerberger et al., CPC 235, 388 (2019)