Preface

Cluster methods for strongly correlated electron systems

“…In the context of disordered system, the dynamical mean field theory has a precursor in the famous coherent potential approximation (CPA) for which cluster extensions such as the molecular CPA [7] have been formulated. Naturally, generalizations of these and other statistical mechanical approaches such as the Bethe Peirls approximation to the area of quantum interacting systems, have been investigated recently [1], [3], [2] , [4] , [8], [6]. This area of investigation is in its beginning stages, and comparative studies of the various methods are important to increase our understanding of the strengths and the limitations of these methods, at a level comparable to our present understanding of the single site dynamical mean field theory.…”

“…This note is a contribution in this direction. We focus, here on the CDMFT [6] and the DCA [2] method, because both methods have been proved to be manifestly causal, i.e. the output of an approximated solution of the cluster equations is causal, as long as a causal method is used for the solution of the impurity model.…”

“…al. [2] after a Fourier transformation with cluster momenta. Once Ĝ0 is known, Ĝc is computed by functional integration of the cluster effective action and the new cluster self-energy is obtained by…”

“Do not kill them, lest my people forget”: Changes in Attitudes Towards Jews in Twelfth- and Thirteenth-Century England

“…Perversely, most English still saw the Jews as the tax-happy king's agents and endorsers, perhaps not realizing or sympathizing with the financial burden of being the king's property. 30 Abusing the Jewish minority would have given an outlet not only to financial woes, but also to war-weariness and anxieties about security as well. English Jews tried to compensate by increasing their money lending operations, which vexed tax-burdened Christians.…”

“…indicate either that Edward became more hostile towards Jews or that he thought there was more money in Jews paying to get out of prison than actual revenue from coin-clipping prosecutions. 33 Paul Brand cogently calls the whole affair a 'sting' operation against the English Jewry. 34 Robert Stacey writes, however, that not all of the anti-Jewish attitudes and policies recorded can be attributed to economics.…”