2015/05/12 by K. Coester, K. P. Schmidt, Kai Phillip Schmidt · 40 citations
Mathematics · Physics and Astronomy · #Additive function #Cluster (spacecraft) #Cluster expansion #Combinatorics #Computer science #Coupled cluster #Coupling constant #Discrete mathematics #Graph #Hamiltonian (control theory) #Mathematical analysis #Mathematical optimization #Mathematics #Physics #Physics of Superconductivity and Magnetism #Quantum #Quantum many-body systems #Quantum mechanics #Theoretical and Computational Physics #Unitary state #Unitary transformation #cond-mat.str-el
paper · pdf · doi:10.1103/physreve.92.022118
published in Physical Review E 92(2), 022118 (American Physical Society) · 13 pages, 7 figures
arxiv created 2015/05/12 · openalex publication_date 2015/08/10 · arxiv updated 2015/09/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We introduce a white-graph expansion for the method of perturbative continuous unitary transformations when implemented as a linked-cluster expansion. The essential idea behind an expansion in white graphs is to perform an optimized bookkeeping during the calculation by exploiting the model-independent effective Hamiltonian in second quantization and the associated inherent cluster additivity. This approach is shown to be especially well suited for microscopic models with many coupling constants, since the total number of relevant graphs is drastically reduced. The white-graph expansion is exemplified for a two-dimensional quantum spin model of coupled two-leg XXZ ladders.