Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 112: Correlated Electrons: (General) Theory 3

TT 112.1: Talk

Friday, March 20, 2015, 09:30–09:45, H 3010

A generalized perspective on non-perturbative linked cluster expansions — Kris Coester¹, Sebastian Clever¹, Frederic Herbst¹, Sylvain Capponi², and •Kai Phillip Schmidt¹ — ¹TU Dortmund, Dortmund, Germany — ²Université Paul Sabatier, Toulouse, France

We identify a fundamental challenge for any non-perturbative approach based on finite clusters resulting from the reduced symmetry on graphs, most importantly the breaking of translational symmetry, when targeting the properties of excited states. A generalized notion of cluster additivity is introduced, which is used to formulate an optimized scheme of graph-based continuous unitary transformations allowing to solve and to physically understand this major issue. Most importantly, it demands to go beyond the paradigm of using the exact eigenvectors on graphs.