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TT: Fachverband Tiefe Temperaturen

TT 51: Correlated Electrons: Method Development II

TT 51.11: Vortrag

Mittwoch, 11. März 2026, 17:45–18:00, HSZ/0101

Renormalised Interactions via Composite Fields — •Oleksandr Sulyma¹, Jan von Delft², and Benedikt Schneider² — ¹Institute for Theoretical Physics, University of Cologne, Cologne, Germany — ²Arnold Sommerfeld Center for Theoretical Physics, Center for NanoScience, and Munich Center for Quantum Science and Technology, Ludwig-Maximilians-University of Munich, Munich, Germany

The renormalised interactions of particles in quantum many-body systems and general field theories are described by the one-particle-irreducible vertices. The numerical calculation and treatment of these objects have proven to be challenging because of their high dimensionality and complicated frequency and momentum structure. To address these problems, multiple solutions have been proposed: a frequency parametrisation using asymptotic classes; the single-boson exchange (SBE) formalism, which uses only physical correlation functions, thereby avoiding vertex divergencies in the parquet formalism; and symmetric estimators which avoid the amputation of Green's functions, to name a few. We present a unified framework based on the inverse Legendre transform of the composite field effective action that generalises asymptotic classes, symmetric improved estimators, the SBE and the parquet formalism. We demonstrate that these representations of the four-point vertex correspond to different choices of composite fields and naturally extend to more general theories and any-order vertices via simple tree diagrams.

Keywords: Parquet; Single-boson; Asymptotic; Estimator; Vertex