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We describe the time-dependent restricted-active-space self-consistent-field (TD-RASSCF) method for a system of interacting bosons. We provide the theory of the method and discuss its numerical implementation. The method provides a general…

Quantum Physics · Physics 2017-04-28 Camille Lévêque , Lars Bojer Madsen

The issue of orbital relaxation in computational core-hole spectroscopy, specifically x-ray absorption, has been a major problem for methods such as equation-of-motion coupled cluster with singles and doubles (EOM-CCSD). The…

Chemical Physics · Physics 2025-03-26 Megan Simons , Devin A. Matthews

Numerically exact continuous-time Quantum Monte Carlo algorithm for finite fermionic systems with non-local interactions is proposed. The scheme is particularly applicable for general multi-band time-dependent correlations since it does not…

Strongly Correlated Electrons · Physics 2009-11-10 A. N. Rubtsov , A. I. Lichtenstein

We propose a novel reduced-order methodology to describe complex multi-frequency fluid dynamics from time-resolved snapshot data. Starting point is the Cluster-based Network Model (CNM) thanks to its fully automatable development and human…

Fluid Dynamics · Physics 2025-07-29 Antonio Colanera , Nan Deng , Matteo Chiatto , Luigi de Luca , Bernd R. Noack

We present a reduced-cost equation-of-motion coupled-cluster method for excited states, built on a new state-specific frozen natural orbital (SS-FNO) framework. This approach enables systematic and controllable truncation of the virtual…

Chemical Physics · Physics 2025-07-24 Amrita Manna , Achintya Kumar Dutta

The time-dependent restricted-active-space self-consistent-field singles (TD-RASSCF-S) method is presented for investigating TD many-electron dynamics in atoms and molecules. Adopting the SCF notion from the muticonfigurational TD…

Atomic Physics · Physics 2014-05-22 Haruhide Miyagi , Lars Bojer Madsen

We present the time-dependent complete-active-space self-consistent-field (TD-CASSCF) method to simulate multielectron dynamics in ultrafast intense laser fields from the first principles. While based on multiconfiguration expansion, it…

Atomic Physics · Physics 2018-04-24 Takeshi Sato , Yuki Orimo , Takuma Teramura , Oyunbileg Tugs , Kenichi L. Ishikawa

A coupled-cluster approach for systems of $N$ bosons in external traps is developed. In the coupled-cluster approach the exact many-body wavefunction is obtained by applying an exponential operator $\exp{T}$ to the ground configuration…

Other Condensed Matter · Physics 2009-11-11 Lorenz S. Cederbaum , Ofir E. Alon , Alexej I. Streltsov

The Coupled Cluster (CC) method is used to compute the electronic correlation energy in atoms and molecules and often leads to highly accurate results. However, due to its single-reference nature, standard CC in its projected form fails to…

Recent years have seen the development of two types of non-local extensions to the single-site dynamical mean field theory. On one hand, cluster approximations, such as the dynamical cluster approximation, recover short-range…

Strongly Correlated Electrons · Physics 2018-03-21 Sergei Iskakov , Hanna Terletska , Emanuel Gull

With growing demand for time-domain simulations of correlated many-body systems, the development of efficient and stable integration schemes for the time-dependent Schr\"odinger equation is of keen interest in modern electronic structure…

Chemical Physics · Physics 2023-08-22 David B. Williams-Young , Stephen Yuwono , A. Eugene DePrince , Chao Yang

The out of time order correlator (OTOC) serves as a powerful tool for investigating quantum information spreading and chaos in complex systems. We present a method employing non-equilibrium dynamical mean-field theory (DMFT) and coherent…

Strongly Correlated Electrons · Physics 2026-02-20 Chakradhar Rangi , Juana Moreno , Ka-Ming Tam

A simple many-fermion system in which there exists N identical fermions in a single spherical orbit with pairing interaction is treated by means of the time-dependent variational approach with a quasi-spin squeezed state with the aim of…

Nuclear Theory · Physics 2007-05-23 Y. Tsue , H. Akaike

The nonequilibrium variational-cluster approach is applied to study the real-time dynamics of the double occupancy in the one-dimensional Fermi-Hubbard model after different fast changes of hopping parameters. A simple reference system,…

Strongly Correlated Electrons · Physics 2016-04-15 Felix Hofmann , Martin Eckstein , Michael Potthoff

In quantum chemistry, one of the most important challenges is the static correlation problem when solving the electronic Schr\"odinger equation for molecules in the Born--Oppenheimer approximation. In this article, we analyze the tailored…

Numerical Analysis · Mathematics 2019-11-21 Fabian M. Faulstich , Andre Laestadius , Örs Legeza , Reinhold Schneider , Simen Kvaal

Exact solutions for local equilibrium and nonequilibrium out-of-time-ordered correlation (OTOC) functions are obtained for a lattice fermion model with on-site interactions, namely the Falicov-Kimball (FK) model, in the large dimensional…

Quantum Gases · Physics 2017-02-13 Naoto Tsuji , Philipp Werner , Masahito Ueda

Quantum periodic cluster methods for strongly correlated electron systems are reformulated and developed. The reformulation and development are based on a canonical transformation which periodizes the fermions in the cluster space. The…

Strongly Correlated Electrons · Physics 2007-05-23 Tran Minh-Tien

We present the time-dependent restricted-active-space self-consistent field (TD-RASSCF) theory as a new framework for the time-dependent many-electron problem. The theory generalizes the multiconfigurational time-dependent Hartree-Fock…

Atomic Physics · Physics 2014-05-22 Haruhide Miyagi , Lars Bojer Madsen

Real-time coupled cluster (CC) methods have several advantages over their frequency-domain counterparts, namely, response and equation of motion CC theories. Broadband spectra, strong fields, and pulse manipulation allow for the simulation…

Chemical Physics · Physics 2023-08-04 Benjamin G. Peyton , Zhe Wang , T. Daniel Crawford

The computation of the nuclear quantum dynamics of molecules is challenging, requiring both accuracy and efficiency to be applicable to systems of interest. Recently, theories have been developed for employing time-dependent basis functions…