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We advance a novel method for the finite-temperature effective action for nonequilibrium quantum fields and find the QED effective action in time-dependent electric fields, where charged pairs evolve out of equilibrium. The imaginary part…

High Energy Physics - Theory · Physics 2014-11-21 Sang Pyo Kim , Hyun Kyu Lee , Yongsung Yoon

An appropriate extension of the effective potential theory is presented that permits the approximate calculation of the dynamical correlation functions for quantum systems. These are obtained by evaluating the generating functionals of the…

Statistical Mechanics · Physics 2007-05-23 A. Cuccoli , V. Tognetti , R. Giachetti , R. Vaia

In this paper, we show that it is possible to significantly boost the heat extraction ability of the ICO fridge by applying N identical thermalising channels in a superposition of N cyclic causal orders[2], and that this can be further…

Quantum Physics · Physics 2022-03-15 Hanlin Nie , Tianfeng Feng , Samuel Longden , Vlatko Vedral

This paper presents a deep Koopman-based Economic Model Predictive Control (EMPC) for efficient operation of a laboratory-scale pasteurization unit (PU). The method uses Koopman operator theory to transform the complex, nonlinear system…

Systems and Control · Electrical Eng. & Systems 2025-11-07 Patrik Valábek , Michaela Horváthová , Martin Klaučo

The approach to the calculation of quantum dynamical correlation functions is presented in the framework of the Mori theory. An unified treatment of classic and quantum dynamics is given in terms of Weyl representation of operators and…

Statistical Mechanics · Physics 2009-10-31 R. Giachetti , R. Maciocco , V. Tognetti

We extend ring-polymer molecular dynamics (RPMD) to allow for the direct simulation of general, electronically non-adiabatic chemical processes. The kinetically constrained (KC) RPMD method uses the imaginary-time path-integral…

Statistical Mechanics · Physics 2014-03-05 Artur R. Menzeleev , Franziska Bell , Thomas F. Miller

A canonical formulation of effective equations describes quantum corrections by the back-reaction of moments on the dynamics of expectation values of a state. As a first step toward an extension to quantum-field theory, these methods are…

High Energy Physics - Theory · Physics 2014-11-14 Martin Bojowald , Suddhasattwa Brahma

Magnetic and electronic properties of the Hubbard model on the Bethe and fcc lattices in infinite dimensions have been investigated numerically on the basis of the dynamical coherent potential approximation (CPA) theory combined with the…

Strongly Correlated Electrons · Physics 2011-04-22 Toshihito Tamashiro , Shota Nohara , Keisuke Miyagi , Yoshiro Kakehashi

We extend and benchmark the recently-developed Effective-Hamiltonian (EFFH) method [PRX Quantum $\bf{4}$, 020307 (2023)] as an approximation to the equilibrium state ("mean-force Gibbs state") of a quantum system at strong coupling to a…

Statistical Mechanics · Physics 2023-10-03 Nicholas Anto-Sztrikacs , Brett Min , Marlon Brenes , Dvira Segal

We consider the certification of temporal quantum correlations using the pseudo-density matrix (PDM), an extension of the density matrix to the time domain, where negative eigenvalues are key indicators of temporal correlations.…

Quantum Physics · Physics 2025-04-25 Hongfeng Liu , Zhenhuan Liu , Shu Chen , Xinfang Nie , Xiangjing Liu , Dawei Lu

The decay rate for a particle in a metastable cubic potential is investigated in the quantum regime by the Euclidean path integral method in semiclassical approximation. The imaginary time formalism allows one to monitor the system as a…

Statistical Mechanics · Physics 2008-04-22 Marco Zoli

We present an effective potential that allows quantum thermal expectation values of a position-dependent observable to be estimated as a classical ensemble average of the corresponding function. We follow the approach of Feynman and Hibbs,…

Quantum Physics · Physics 2026-02-16 Vijay Ganesh Sadhasivam , Stuart C. Althorpe , Venkat Kapil

Stochastic Analytic Continuation (SAC) of Quantum Monte Carlo (QMC) imaginary-time correlation function data is a valuable tool in connecting many-body models to experimentally measurable dynamic response functions. Recent developments of…

Strongly Correlated Electrons · Physics 2024-11-26 Gabe Schumm , Sibin Yang , Anders W. Sandvik

The Quantum Monte Carlo (QMC) method can yield the imaginary-time dependence of a correlation function $C(\tau)$ of an operator $\hat O$. The analytic continuation to real-time proceeds by means of a "numerical inversion" of these data to…

Strongly Correlated Electrons · Physics 2015-03-11 Nikolaos G. Diamantis , Efstratios Manousakis

The exact exchange potential in time-dependent density-functional theory is defined as an orbital functional through the time-dependent optimized effective potential (TDOEP) method. We numerically solve the TDOEP integral equation for the…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 H. O. Wijewardane , C. A. Ullrich

We develop a framework for simulating measure-preserving, ergodic dynamical systems on a quantum computer. Our approach provides a new operator-theoretic representation of classical dynamics by combining ergodic theory with quantum…

Feynman path integrals (PIs) have found many uses in approximate quantum dynamics methods that are able to efficiently calculate real-time quantum correlation functions. The PIs typically take the form of discrete imaginary time slices over…

Chemical Physics · Physics 2025-10-14 Nathan London , Mohammad R. Momeni

Entropic dynamics (ED) is a framework that allows one to derive quantum theory as a Hamilton-Killing flow on the cotangent bundle of a statistical manifold. These flows are such that they preserve the symplectic and the (information) metric…

Quantum Physics · Physics 2025-11-25 Ariel Caticha

We outline ideas on desired properties for a new generation of effective core potentials (ECPs) that will allow valence-only calculations to reach the full potential offered by recent advances in many-body wave function methods. The key…

Critical decisions frequently rely on high-dimensional output from complex computer simulation models that show intricate cross-variable, spatial and temporal dependence structures, with weather and climate predictions being key examples.…

Methodology · Statistics 2013-12-24 Roman Schefzik , Thordis L. Thorarinsdottir , Tilmann Gneiting