Numerical Renormalization Group Calculations for the Self-energy of the impurity Anderson model

We present a new method to calculate directly the one-particle self-energy of an impurity Anderson model with Wilson's numerical Renormalization Group method by writing this quantity as the ratio of two correlation functions. This way of calculating Sigma(z) turns out to be considerably more reliable and accurate than via the impurity Green's function alone. We show results for the self-energy for the case of a constant coupling between impurity and conduction band (ImDelta = const) and the effective Delta(z) arising in the Dynamical Mean Field Theory of the Hubbard model. Implications to the problem of the metal-insulator transition in the Hubbard model are also discussed.Comment: 18 pages, 9 figures, submitted to J. Phys.: Condens. Matte

The low-energy scale of the periodic Anderson model

Wilson's Numerical Renormalization Group method is used to study the paramagnetic ground state of the periodic Anderson model within the dynamical mean-field approach. For the particle-hole symmetric model, which is a Kondo insulator, we find that the lattice Kondo scale T_0 is strongly enhanced over the impurity scale T_K; T_0/T_K ~ exp(1/3I), where I is the Schrieffer-Wolff exchange coupling. In the metallic regime, where the conduction band filling is reduced from one, we find characteristic signatures of Nozi\`eres exhaustion scenario, including a strongly reduced lattice Kondo scale, a significant suppression of the states available to screen the f-electron moment, and a Kondo resonance with a strongly enhanced height. However, in contrast to the quantitative predictions of Nozi\`eres, we find that the T_0 ~ T_K with a coefficient which depends strongly on conduction band filling.Comment: 11 pages, 9 figures, submitted to Phys. Rev.

Exakte Ergebnisse zum Falicov-Kimball-Modell in hohen Dimensionen

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Water and the display of power in Augustan Rome: the so-called ‘Villa Claudia’ at Anguillara Sabazia

This article re-considers the architecture of the Roman villa site at Anguillara Sabazia (Lazio (RM), Italy). It is argued that the villa should be dated to the Augustan period, rather than the late Republic, and that its elaborate ornamental water features, including fountains arranged in an elliptical curve, were supplied by the Augustan aqueduct, the Aqua Alsietina, also known as the Aqua Augusta, either directly, or through a subsidiary branch off the main conduit. Its particular elliptical form, unique in Roman villa architecture at that time, may be explained as a small-scale version of the imperial pool (Stagnum) created in 2 bc for the Emperor Augustus’s recreation of sea-battles (Naumachia Augusti) in the modern district of Trastevere, which was the eventual destination of the aqueduct. There is no firm evidence for the owner of the villa, but a fragment of an honorific inscription from the site suggests a high-ranking ex-consul from the family of the Cornelii, possibly connected with the water administration (Cura Aquarum) in Rome