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We describe a method to obtain the reduced density matrix (RDM) correct up to second order in system-bath coupling in \emph{nonequilibrium} steady state situations. The RDM is obtained via a scheme based on analytic continuation, using the…

Statistical Mechanics · Physics 2013-11-22 Juzar Thingna , Jian-Sheng Wang , Peter Hänggi

We present a new approach to calculate real-time quantum dynamics in complex systems. The formalism is based on the partitioning of a system's environment into "core" and "reservoir" modes, with the former to be treated quantum mechanically…

Statistical Mechanics · Physics 2015-05-30 Timothy C. Berkelbach , David R. Reichman , Thomas E. Markland

It is argued that cluster methods provide a viable alternative to Wilson's momentum shell integration technique at the early stage of renormalization in the field-theoretic models with strongly coupled fields because these methods allow for…

Statistical Mechanics · Physics 2016-06-23 V. I. Tokar

We present a novel real-space renormalization group(RG) for the one-dimensional XXZ model in the critical regime, reconsidering the role of the cut-off parameter in Wilson's RG for the Kondo impurity problem. We then demonstrate the RG…

Statistical Mechanics · Physics 2008-11-26 Kouichi Okunishi

The time-dependent numerical renormalization-group approach (TD-NRG), originally devised for tracking the real-time dynamics of quantum-impurity systems following a single quantum quench, is extended to multiple switching events. This…

Mesoscale and Nanoscale Physics · Physics 2012-06-12 Eitan Eidelstein , Avraham Schiller , Fabian Guettge , Frithjof B. Anders

We introduce a new numerical method for the solution of self-consistent equations in the cluster mean-field theory. The method uses the density matrix renormalization group method to solve the associated cluster problem. We obtain an…

Quantum Gases · Physics 2014-11-10 Ryota Suzuki , Akihisa Koga

We apply a recently developed nonequilibrium real-time renormalization group method in frequency space to describe nonlinear quantum transport through a small fermionic quantum system coupled weakly to several reservoirs via spin and/or…

Mesoscale and Nanoscale Physics · Physics 2009-07-23 Herbert Schoeller , Frank Reininghaus

The Anderson impurity model (AIM) has long served as a cornerstone in the study of correlated electron systems. While numerical renormalization group (RG) offers great flexibility for metallic reservoirs, it becomes impossible in an…

Strongly Correlated Electrons · Physics 2025-07-24 Peter Zalom

Quantum impurity models describe interactions between some local degrees of freedom and a continuum of non-interacting fermionic or bosonic states. The investigation of quantum impurity models is a starting point towards the understanding…

Strongly Correlated Electrons · Physics 2008-09-19 O. Legeza , C. P. Moca , A. I. Toth , I. Weymann , G. Zarand

We extend the numerical renormalization-group method to Bose-Fermi Kondo models (BFKMs), describing a local moment coupled to a conduction band and a dissipative bosonic bath. We apply the method to the Ising-symmetry BFKM with a bosonic…

Strongly Correlated Electrons · Physics 2016-08-31 Matthew T. Glossop , Kevin Ingersent

A numerical renormalization group technique based on Wilson's momentum shell method is presented for interacting, finite fermi systems. Results for small fullerene analogs show that the method is quite accurate to moderate values of $U$,…

Condensed Matter · Physics 2009-10-22 T. Tokuyasu , M. Kamal , G. Murthy

In these lecture notes, we present a pedagogical review of a number of related {\it numerically exact} approaches to quantum many-body problems. In particular, we focus on methods based on the exact diagonalization of the Hamiltonian matrix…

Strongly Correlated Electrons · Physics 2007-05-23 Reinhard M. Noack , Salvatore R. Manmana

We propose a numerical renormalization group (NRG) approach to steady-state currents through nano-devices. A discretization of the scattering-states continuum ensures the correct boundary condition for an open quantum system. We introduce…

Mesoscale and Nanoscale Physics · Physics 2009-01-15 Frithjof B. Anders

A new numerical method for the solution of the Dynamical Mean Field Theory's self-consistent equations is introduced. The method uses the Density Matrix Renormalization Group technique to solve the associated impurity problem. The new…

Strongly Correlated Electrons · Physics 2016-08-31 Daniel J. Garcia , Karen Hallberg , Marcelo J. Rozenberg

Wilson's Numerical Renormalization Group (NRG) is so far the only nonperturbative technique that can reliably access low-energy properties of quantum impurity systems. We present a recent extension of the method, the DM-NRG, which yields…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 Walter Hofstetter

Many quantum mechanical problems (such as dissipative phase fluctuations in metallic and superconducting nanocircuits, or impurity scattering in Luttinger liquids) involve a continuum of bosonic modes with a marginal spectral density…

Strongly Correlated Electrons · Physics 2011-11-07 Axel Freyn , Serge Florens

We discuss the relation between the Wilson's numerical renormalization group(NRG) for the Kondo impurity problem and a field theory in the background AdS_3 space time, where the radial coordinate plays a role of the controlling parameter of…

High Energy Physics - Theory · Physics 2012-08-09 Kouichi Okunishi

We present a real-space renormalization group approach for the corner Hamiltonian, which is relevant to the reduced density matrix in the density matrix renormalization group. A set of self-consistent equations that the renormalized…

Statistical Mechanics · Physics 2007-05-23 Kouichi Okunishi

We present a hybrid numerical approach to simulate quantum many body problems on two spatial dimensional quantum lattice models via the non-Abelian ab initio version of the density matrix renormalization group method on state-of-the-art…

Strongly Correlated Electrons · Physics 2024-06-05 Andor Menczer , Kornél Kapás , Miklós Antal Werner , Örs Legeza

We develop a Markovian master equation in the Lindblad form that enables the efficient study of a wide range of open quantum many-body systems that would be inaccessible with existing methods. The validity of the master equation is based…

Mesoscale and Nanoscale Physics · Physics 2020-09-08 Frederik Nathan , Mark S. Rudner