2003/06/30 by Satoshi Okamoto, S. Okamoto, Andrew J. Millis +5 · 3 citations
Physics and Astronomy · #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Theoretical and Computational Physics #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.68.195121
arxiv created 2003/08/26 · openalex publication_date 2003/11/26 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
``Cluster'' extensions of the dynamical mean-field method to include longer-range correlations are discussed. It is argued that the clusters arising in these methods are naturally interpreted not as actual subunits of a physical lattice but as algorithms for computing coefficients in an orthogonal function expansion of the momentum dependence of the electronic self-energy. The difficulties with causality which have been found to plague cluster dynamical mean-field methods are shown to be related to the ``ringing'' phenomenon familiar from Fourier analysis. The analogy is used to motivate proposals for simple filtering methods to circumvent them. The formalism is tested by comparison to low-order perturbative calculations and self-consistent solutions.