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The theory of real-time quantum many-body dynamics as put forward in Ref. [arXiv:0710.4627] is evaluated in detail. The formulation is based on a generating functional of correlation functions where the Keldysh contour is closed at a given…

Quantum Gases · Physics 2011-02-09 Thomas Gasenzer , Stefan Kessler , Jan M. Pawlowski

Standard derivations of the functional integral in non-equilibrium quantum field theory are based on the discrete time representation. In this work we derive the non-equilibrium functional integral for non-interacting bosons and fermions…

Mathematical Physics · Physics 2015-02-27 Filippo Bovo

Nonequilibrium quantum mechanics can be solved with the Keldysh formalism, which evolves the quantum mechanical states forward in time in the presence of a time-dependent field, and then evolves them backward in time, undoing the effect of…

Strongly Correlated Electrons · Physics 2007-05-23 J. K. Freericks , V. Turkowski , V. Zlatic

This review deals with the nonequilibrium Green's function (NEGF) method applied to the problems of energy transport due to atomic vibrations (phonons), primarily for small junction systems. We present a pedagogical introduction to the…

Mesoscale and Nanoscale Physics · Physics 2013-05-28 Jian-Sheng Wang , Bijay Kumar Agarwalla , Huanan Li , Juzar Thingna

We derive equations of motion for higher order density response functions using the theory of thermodynamic Green's functions. We also derive expressions for the higher order generalized dielectric functions and polarization functions.…

Strongly Correlated Electrons · Physics 2024-10-04 Jan Vorberger , Tobias Dornheim , Maximilian P. Böhme , Zhandos Moldabekov , Panagiotis Tolias

We extend the self-consistent Green's functions formalism to take into account three-body interactions. We analyze the perturbative expansion in terms of Feynman diagrams and define effective one- and two-body interactions, which allows for…

Nuclear Theory · Physics 2013-12-03 Arianna Carbone , Andrea Cipollone , Carlo Barbieri , Arnau Rios , Artur Polls

For thermal equilibrium systems it is shown, how the Kubo-Martin-Schwinger boundary condition may be used to factorize the generating functional of Green functions at least on the level of the full two-point function. Genuine…

High Energy Physics - Phenomenology · Physics 2007-05-23 P. A. Henning , R. Fauser

Inertial effects in fluctuations of the work to sustain a system in a nonequilibrium steady state are discussed for a dragged massive Brownian particle model using a path integral approach. We calculate the work distribution function in the…

Statistical Mechanics · Physics 2007-12-12 Tooru Taniguchi , E. G. D. Cohen

The transport and gain properties of quantum cascade (QC) structures are investigated using a nonequilibrium Green's function (NGF) theory which includes quantum effects beyond a Boltzmann transport description. In the NGF theory, we…

Mesoscale and Nanoscale Physics · Physics 2009-11-07 S. -C. Lee , A. Wacker

We present an implementation of the steady state Keldysh approach in a Green's function multiple scattering scheme to calculate the non-equilibrium spin density. This density is used to obtain the spin transfer torque in junctions showing…

Mesoscale and Nanoscale Physics · Physics 2008-02-13 Christian Heiliger , Michael Czerner , Bogdan Yu. Yavorsky , Ingrid Mertig , Mark D. Stiles

A quantum transport model incorporating spin scattering processes is presented using the non-equilibrium Green's function (NEGF) formalism within the self-consistent Born approximation. This model offers a unified approach by capturing the…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 Ahmet Ali Yanik , Gerhard Klimeck , Supriyo Datta

The Non-Equilibrium Green Function (NEGF) method was established in the 1960's through the classic work of Schwinger, Kadanoff, Baym, Keldysh and others using many-body perturbation theory (MBPT) and the diagrammatic theory for…

Mesoscale and Nanoscale Physics · Physics 2022-11-24 Kerem Y. Camsari , Shuvro Chowdhury , Supriyo Datta

We propose an experimental scheme to verify the quantum non-equilibrium fluctuation relations using current technology. Specifically, we show that the characteristic function of the work distribution for a non-equilibrium quench of a…

Quantum Physics · Physics 2013-06-18 R. Dorner , S. R. Clark , L. Heaney , R. Fazio , J. Goold , V. Vedral

The work distribution function for a non-relativistic, non-interacting quantum many-body system interacting with classical external sources is investigated. Exact expressions for the characteristic function corresponding to the work…

Quantum Physics · Physics 2020-04-22 Fardin Kheirandish

We study the statistics of work, dissipation, and entropy production of a quantum quasi-isothermal process, where the system remains close to the thermal equilibrium along the transformation. We derive a general analytic expression for the…

Quantum Physics · Physics 2020-07-01 Matteo Scandi , Harry J. D. Miller , Janet Anders , Marti Perarnau-Llobet

At non-zero temperature classical systems exhibit statistical fluctuations of thermodynamic quantities arising from the variation of the system's initial conditions and its interaction with the environment. The fluctuating work, for…

Quantum Physics · Physics 2018-02-07 Rui Sampaio , Samu Suomela , Tapio Ala-Nissila , Janet Anders , Thomas Philbin

The increasing interest in nonequilibrium effects in condensed matter theory motivates the adaption of diverse equilibrium techniques to Keldysh formalism. For methods based on multi-particle Green or vertex functions this involves a…

Strongly Correlated Electrons · Physics 2010-03-03 Severin G. Jakobs , Mikhail Pletyukhov , Herbert Schoeller

The quantum dynamics of fermionic or bosonic many-body systems following external excitation can be successfully studied using two-time nonequilibrium Green's functions (NEGF) or single-time reduced density matrix methods. Approximations…

Strongly Correlated Electrons · Physics 2022-07-12 Erik Schroedter , Jan-Philip Joost , Michael Bonitz

We develop a theoretical framework to determine distribution functions in nonequilibrium systems coupled to equilibrium reservoirs, by using the nonequilibrium Green's function technique. As a paradigmatic example, we consider the…

Mesoscale and Nanoscale Physics · Physics 2026-02-05 Taira Kawamura , Yusuke Kato

We present a quantum kinetic approach for the time-resolved description of many-body effects in photoionization processes in atoms. The method is based on the non-equilibrium Green functions formalism and solves the Keldysh/Kadanoff-Baym…

Atomic Physics · Physics 2015-05-13 D. Hochstuhl , K. Balzer , S. Bauch , M. Bonitz