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We study a pseudogap region of the mixed boson fermion system using a recent formulation of the renormalization group technique through the set of infinitesimal unitary transformations. Renormalization of fermion energies gives rise to a…

Superconductivity · Physics 2016-08-31 T. Domanski , J. Ranninger

The fluctuation exchange (FLEX) approximation is applied to study the Holstein-Hubbard model. Due to the retarded nature of the phonon-mediated electron-electron interaction, neither fast Fourier transform (FFT) nor previously developed NRG…

Strongly Correlated Electrons · Physics 2009-10-31 C. -H. Pao , H. -B. Schuttler

The Similarity Renormalization Group (SRG) is investigated as a powerful yet practical method to modify nuclear potentials so as to reduce computational requirements for calculations of observables. The key feature of SRG transformations…

Nuclear Theory · Physics 2009-12-16 E. D. Jurgenson

We review the functional renormalization group (RG) approach to the BCS-BEC crossover for an ultracold gas of fermionic atoms. Formulated in terms of a scale-dependent effective action, the functional RG interpolates continuously between…

Quantum Gases · Physics 2010-10-15 Michael M. Scherer , Stefan Floerchinger , Holger Gies

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 develop a new formulation of the functional renormalization group (RG) for interacting fermions. Our approach unifies the purely fermionic formulation based on the Grassmannian functional integral, which has been used in recent years by…

Strongly Correlated Electrons · Physics 2007-05-23 Florian Schuetz , Lorenz Bartosch , Peter Kopietz

Inspired by the superblock method of White, we introduce a simple modification of the standard Renormalization Group (RG) technique for the study of quantum lattice systems. Our method which takes into account the effect of Boundary…

Statistical Mechanics · Physics 2009-10-28 A. Langari , V. Karimipour

We analyze the one-dimensional extended Hubbard model with a single static impurity by using a computational technique based on the functional renormalization group. This extends previous work for spinless fermions to spin-1/2 fermions. The…

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

The Lieb-Robinson bound implies that the unitary time evolution of an operator can be restricted to an effective light cone for any Hamiltonian with short-range interactions. Here we present a very efficient renormalization group algorithm…

Strongly Correlated Electrons · Physics 2015-03-19 Tilman Enss , Jesko Sirker

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

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

The problem of weakly correlated electrons on a square lattice is formulated in terms of one-loop renormalization group. Starting from the action for the entire Brillouin zone (and not with a low-energy effective action) we reduce…

Condensed Matter · Physics 2009-10-28 D. Zanchi , H. J. Schulz

We implement an explicit two-loop calculation of the coupling functions and the self-energy of interacting fermions with a two-dimensional flat Fermi surface in the framework of the field theoretical renormalization group (RG) approach.…

Strongly Correlated Electrons · Physics 2009-11-10 H. Freire , E. Correa , A. Ferraz

We study transport properties of quantum impurity systems using the functional renormalization group. The latter is an RG-based diagrammatic tool to treat Coulomb interactions in a fast and flexible way. Prior applications, which employed a…

Strongly Correlated Electrons · Physics 2010-09-21 C. Karrasch

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

The method of functional renormalization is applied to the theoretical investigation of ultracold quantum gases. Flow equations are derived for a Bose gas with approximately pointlike interaction, for a Fermi gas with two (hyperfine) spin…

Quantum Gases · Physics 2015-05-14 S. Floerchinger

A renormalization group (RG) analysis of the superconductive instability of an anisotropic fermionic system is developed at a finite temperature. The method appears a natural generalization of Shankar's approach to interacting fermions and…

Condensed Matter · Physics 2009-10-28 Fabio Siringo , Giuseppe G. N. Angilella , Renato Pucci

We study weakly-repulsive Bose-Bose mixtures in two and three dimensions at zero temperature using the functional renormalization group (FRG). We examine the RG flows and the role of density and spin fluctuations. We study the condition for…

Quantum Gases · Physics 2021-01-26 Felipe Isaule , Ivan Morera , Artur Polls , Bruno Juliá-Díaz

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

We present a functional renormalization group analysis of superconductivity in the ground state of the attractive Hubbard model on a square lattice. Spontaneous symmetry breaking is treated in a purely fermionic setting via anomalous…

Strongly Correlated Electrons · Physics 2009-11-13 R. Gersch , C. Honerkamp , W. Metzner