Gukelberger, Jan Huang, Li Werner, Philipp 2015-06-09 We study the two-dimensional Hubbard model in the weak-coupling regime and compare the self-energy obtained from various approximate diagrammatic schemes to the result of diagrammatic Monte Carlo simulations, which sum up all weak-coupling diagrams up to a given order. While dynamical mean-field theory provides a good approximation for the local part of the self-energy, including its frequency dependence, the partial summation of bubble and/or ladder diagrams typically yields worse results than second-order perturbation theory. Even widely used self-consistent schemes such as GW or the fluctuation-exchange approximation (FLEX) are found to be unreliable. Combining the dynamical mean-field self-energy with the nonlocal component of GW in GW + DMFT yields improved results for the local self-energy and nonlocal self-energies of the correct order of magnitude, but here, too, a more reliable scheme is obtained by restricting the nonlocal contribution to the second-order diagram. FLEX + DMFT is found to give accurate results in the low-density regime, but even worse results than FLEX near half-filling. application/pdf https://folia.unifr.ch/global/documents/304534 https://folia.unifr.ch/documents/304534/files/wer_odp.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevB.91.235114 info:eu-repo/semantics/openAccess License undefined Physical Review B. - 2015, vol. 91, no. 23, p. 235114 info:eu-repo/classification/udc/53 On the dangers of partial diagrammatic summations: Benchmarks for the two-dimensional Hubbard model in the weak-coupling regime http://purl.org/coar/resource_type/c_6501