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We improve the recently developed functional renormalization group (fRG) for impurities and boundaries in Luttinger liquids by including renormalization of the two-particle interaction, in addition to renormalization of the impurity…

Strongly Correlated Electrons · Physics 2007-05-23 S. Andergassen , T. Enss , V. Meden , W. Metzner , U. Schollwoeck , K. Schoenhammer

Within the Functional Renormalisation Group (FRG) approach, we present a fluid-dynamical approach to solving flow equations for models living in a multi-dimensional field space. To this end, the underlying exact flow equation of the…

Statistical Mechanics · Physics 2024-12-23 Niklas Zorbach , Adrian Koenigstein , Jens Braun

We investigate several fundamental characteristics of the multiloop functional renormalization group (mfRG) flow by hands of its application to a prototypical many-electron system: the Anderson impurity model (AIM). We first analyze the…

Strongly Correlated Electrons · Physics 2022-04-22 Patrick Chalupa-Gantner , Fabian B. Kugler , Cornelia Hille , Jan von Delft , Sabine Andergassen , Alessandro Toschi

We present a unified C++ implementation of the functional renormalization group and the parquet equations within the single-boson exchange formalism for several paradigmatic tight-binding and impurity models at equilibrium. The…

Strongly Correlated Electrons · Physics 2026-04-07 Aiman Al-Eryani , Miriam Patricolo , Kilian Fraboulet

We provide a detailed exposition of our computational framework designed for the accurate calculation of real-frequency dynamical correlation functions of the single-impurity Anderson model (AM) in the regime of weak to intermediate…

Strongly Correlated Electrons · Physics 2026-01-27 Nepomuk Ritz , Anxiang Ge , Elias Walter , Santiago Aguirre , Jan von Delft , Fabian B. Kugler

We consider quantum electrodynamics with chiral four-Fermi interactions in the functional renormalization group approach. In gauge theories, the functional flow equation for the effective action is accompanied by the quantum master equation…

High Energy Physics - Theory · Physics 2026-01-14 Yoshio Echigo , Yuji Igarashi , Katsumi Itoh , Jan M. Pawlowski , Yu Takahashi

We describe how the fermionic functional renormalization group (fRG) flow of a Cooper+forward scattering problem can be continued into the superconducting state. This allows us to reproduce from the fRG flow the fundamental equations of the…

Superconductivity · Physics 2009-11-11 Carsten Honerkamp , Manfred Salmhofer

We demonstrate how to devise a Matsubara-formalism-based one-loop approximation to the flow of the functional renormalization group (FRG) that reproduces identically the leading-logarithmic parquet approximation. This construction of a…

Strongly Correlated Electrons · Physics 2024-03-25 Jan Diekmann , Severin G. Jakobs

A formalism for electronic-structure calculations is presented that is based on the functional renormalization group (FRG). The traditional FRG has been formulated for systems that exhibit a translational symmetry with an associated Fermi…

Materials Science · Physics 2016-10-12 Christian Seiler , Ferdinand Evers

We present a recently-developed renormalization group scheme, the functional renormalization group (fRG), as a many-particle method suited to account for the two-particle interactions between the electrons in complex quantum dot geometries.…

Strongly Correlated Electrons · Physics 2007-05-23 C. Karrasch

We derive an expansion of the functional renormalization (fRG) equations that treats the frequency and momentum dependencies of the vertices in a systematic manner. The scheme extends the channel-decomposed fRG equations to the frequency…

Strongly Correlated Electrons · Physics 2021-07-07 Nahom K. Yirga , David K. Campbell

We present a functional renormalization group flow for many-fermion lattice models into phases with broken spin-rotational symmetry. The flow is expressed purely in terms of fermionic vertex functions. The symmetry breaking is seeded by a…

Strongly Correlated Electrons · Physics 2012-10-11 Stefan A. Maier , Carsten Honerkamp

We derive functional renormalization group schemes for Fermi systems which are based on the two-particle irreducible approach to the quantum many-body problem. In a first step, the cutoff is introduced in the non-interacting propagator as…

Strongly Correlated Electrons · Physics 2015-03-25 Jan Frederik Rentrop , Severin Georg Jakobs , Volker Meden

The renormalization group plays an essential role in many areas of physics, both conceptually and as a practical tool to determine the long-distance low-energy properties of many systems on the one hand and on the other hand search for…

Statistical Mechanics · Physics 2021-05-10 N. Dupuis , L. Canet , A. Eichhorn , W. Metzner , J. M. Pawlowski , M. Tissier , N. Wschebor

We consider formulations of the functional renormaliztion-group flow for correlated electronic systems, having the dynamical mean-field theory as a starting point. We classify the corresponding renormalization-group schemes into those…

Strongly Correlated Electrons · Physics 2015-08-04 A. A. Katanin

We present a multiloop pseudofermion functional renormalization group (pffRG) approach to quantum spin systems. As a test case, we study the spin-$\tfrac{1}{2}$ Heisenberg model on the kagome lattice, a prime example of a geometrically…

Strongly Correlated Electrons · Physics 2020-11-04 Julian Thoenniss , Marc K. Ritter , Fabian B. Kugler , Jan von Delft , Matthias Punk

We present a general frame to extend functional renormalization group (fRG) based computational schemes by using an exactly solvable interacting reference problem as starting point for the RG flow. The systematic expansion around this…

Strongly Correlated Electrons · Physics 2015-02-11 Nils Wentzell , Ciro Taranto , Andrey A. Katanin , Alessandro Toschi , Sabine Andergassen

We sketch the construction of a gauge invariant Exact Renormalization Group (ERG). Starting from Polchinski's equation, the emphasis is on how a series of ideas have combined to yield the gauge invariant formalism. A novel symmetry of the…

High Energy Physics - Theory · Physics 2007-05-23 Oliver J. Rosten , Tim R. Morris , Stefano Arnone

We set up the Functional Renormalisation Group formalism for Tensorial Group Field Theory in full generality. We then apply it to a rank-3 model over U(1) x U(1) x U(1), endowed with a linear kinetic term and nonlocal interactions. The…

High Energy Physics - Theory · Physics 2015-07-09 Dario Benedetti , Joseph Ben Geloun , Daniele Oriti

We present an alternative functional renormalization group (fRG) approach to the single-impurity Anderson model at finite temperatures. Starting with the exact self-energy and interaction vertex of a small system ('core') containing a…

Strongly Correlated Electrons · Physics 2013-01-11 Michael Kinza , Jutta Ortloff , Johannes Bauer , Carsten Honerkamp