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The functional renormalization group (fRG) approach has the property that, in general, the flow equation for the two-particle vertex generates $\mathcal{O}(N^4)$ independent variables, where $N$ is the number of interacting states (e.g.…

Strongly Correlated Electrons · Physics 2014-01-24 Florian Bauer , Jan Heyder , Jan von Delft

The functional renormalization group (FRG) has been used widely to investigate phase diagrams, in particular the one of the two-dimensional Hubbard model. So far, the study of one-dimensional models has not attracted as much attention. We…

Strongly Correlated Electrons · Physics 2018-06-18 Lisa Markhof , Björn Sbierski , Volker Meden , Christoph Karrasch

We perform a data-driven dimensionality reduction of the scale-dependent 4-point vertex function characterizing the functional Renormalization Group (fRG) flow for the widely studied two-dimensional $t - t'$ Hubbard model on the square…

We introduce an equilibrium formulation of the functional renormalization group (fRG) for inhomogeneous systems capable of dealing with spatially finite-ranged interactions. In the general third order truncated form of fRG, the dependence…

Strongly Correlated Electrons · Physics 2017-01-17 Lukas Weidinger , Florian Bauer , Jan von Delft

Although the functional renormalization group (fRG) is by now a well-established method for investigating correlated electron systems, it is still undergoing significant technical and conceptual improvements. In particular, the motivation…

Strongly Correlated Electrons · Physics 2018-05-09 G. A. H. Schober , J. Ehrlich , T. Reckling , C. Honerkamp

The functional renormalization group (FRG) provides a flexible tool to study correlations in low-dimensional electronic systems. In this paper, we present a novel FRG approach to the steady-state of quantum wires out of thermal equilibrium.…

Strongly Correlated Electrons · Physics 2020-12-08 Christian Klöckner , Dante Marvin Kennes , Christoph Karrasch

We derive an efficient method for treating renormalization contributions at two-loop level within the functional renormalization group in the one-particle irreducible formalism for fermions. It is based on a decomposition of the…

Strongly Correlated Electrons · Physics 2014-09-16 Andreas Eberlein

Functional renormalization group (FRG) has become a diverse and powerful tool to derive effective low-energy scattering vertices of interacting many-body systems. Starting from a non-interacting expansion point of the action, the flow of…

Strongly Correlated Electrons · Physics 2014-01-22 Johannes Reuther , Ronny Thomale

We introduce the spectrum bifurcation renormalization group (SBRG) as a generalization of the real-space renormalization group for the many-body localized (MBL) system without truncating the Hilbert space. Starting from a disordered…

Strongly Correlated Electrons · Physics 2016-04-06 Yi-Zhuang You , Xiao-Liang Qi , Cenke Xu

Numerous correlated electron systems exhibit a strongly scale-dependent behavior. Upon lowering the energy scale, collective phenomena, bound states, and new effective degrees of freedom emerge. Typical examples include (i) competing…

Strongly Correlated Electrons · Physics 2015-05-28 Walter Metzner , Manfred Salmhofer , Carsten Honerkamp , Volker Meden , Kurt Schoenhammer

A one-dimensional system of bosons with short-range repulsion and mid-range attraction is used as a laboratory to explore the evolution of many-body forces by the Similarity Renormalization Group (SRG). The free-space SRG is implemented for…

Nuclear Theory · Physics 2009-02-12 E. D. Jurgenson , R. J. Furnstahl

We extend the recently introduced single-boson exchange formulation to the computation of the self-energy from the Schwinger--Dyson equation (SDE). In particular, we derive its expression both in diagrammatic and in physical channels. The…

We investigate the phase diagram of a one-dimensional dissipative Bose-Hubbard model using the nonperturbative functional renormalization group (FRG). Each lattice site is coupled to an independent bath, generating long-range temporal…

Quantum Gases · Physics 2026-05-05 Oscar Bouverot-Dupuis , Vincent Grison , Nicolas Paris

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

The pseudofermion functional renormalization group (pffRG) is a computational method for determining zero-temperature phase diagrams of frustrated quantum magnets. In a recent methodological advance, the commonly employed Katanin truncation…

Strongly Correlated Electrons · Physics 2022-07-04 Marc K. Ritter , Dominik Kiese , Tobias Müller , Fabian B. Kugler , Ronny Thomale , Simon Trebst , Jan von Delft

Using the dynamical mean-field theory (DMFT) as a `booster-rocket', the functional renormalization group (fRG) can be upgraded from a weak-coupling method to a powerful computation tool for strongly interacting fermion systems. The strong…

Strongly Correlated Electrons · Physics 2019-03-13 Demetrio Vilardi , Ciro Taranto , Walter Metzner

We propose new approach for treatment of local and non-local interactions in correlated electronic systems, which uses self-energy and the two-particle irreducible vertices, obtained from (extended) dynamical mean-field theory, as an input…

Strongly Correlated Electrons · Physics 2019-03-12 A. A. Katanin

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 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

The functional renormalisation group (fRG) has evolved into a versatile tool in condensed matter theory for studying important aspects of correlated electron systems. Practical applications of the method often involve a high numerical…

Computational Physics · Physics 2016-09-21 Daniel Rohe