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An externally corrected coupled cluster (CC) method, where an adaptive configuration interaction (ACI) wave function provides the external cluster amplitudes, named ACI-CC, is presented. By exploiting the connection between configuration…

Chemical Physics · Physics 2023-09-27 Gustavo J. R. Aroeira , Madeline M. Davis , Justin M. Turney , Henry F. Schaefer

This paper proposes a task-driven computational framework for assessing diffusion MRI experimental designs which, rather than relying on parameter-estimation metrics, directly measures quantitative task performance. Traditional…

Medical Physics · Physics 2021-10-12 Sean C. Epstein , Timothy J. P. Bray , Margaret A. Hall-Craggs , Hui Zhang

White's density matrix renormalization group ({DMRG}) method has been applied to the one-dimensional Ising model in a transverse field ({ITF}), in order to study the accuracy of the numerical algorithm. Due to the exact solubility of the…

Strongly Correlated Electrons · Physics 2009-10-31 Ors Legeza , Gabor Fath

DFT calculations have become widespread in both chemistry and materials, because they usually provide useful accuracy at much lower computational cost than wavefunction-based methods. All practical DFT calculations require an approximation…

Chemical Physics · Physics 2022-03-15 Eunji Sim , Suhwan Song , Stefan Vuckovic , Kieron Burke

This letter investigates the challenge of channel estimation in a multiuser millimeter-wave (mmWave) time-division duplexing (TDD) system. In this system, the base station (BS) employs a multi-antenna uniform linear array (ULA), while each…

Information Theory · Computer Science 2024-01-04 Hao Xu , Gui Zhou , Kai-Kit Wong , Wee Kiat New , Chao Wang , Chan-Byoung Chae , Ross Murch , Shi Jin , Yangyang Zhang

Most methods tackling the phase retrieval problem of magnitude-only antenna measurements suffer from unrealistic sampling requirements, from unfeasible computational complexities, and, most severely, from the lacking reliability of…

Signal Processing · Electrical Eng. & Systems 2022-02-01 Alexander Paulus , Josef Knapp , Jonas Kornprobst , Thomas F. Eibert

The paper investigates a variant of semi-implicit spectral deferred corrections (SISDC) in which the stiff, fast dynamics correspond to fast propagating waves ("fast-wave slow-wave problem"). We show that for a scalar test problem with two…

Numerical Analysis · Mathematics 2016-08-18 Daniel Ruprecht , Robert Speck

Traditional multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) methods are based on a single orthonormal orbital basis (OB). For atoms with complicated shell structures, a large OB is needed to saturate all the…

Atomic Physics · Physics 2015-06-12 S. Verdebout , P. Rynkun , P. Jönsson , G. Gaigalas , C. Froese Fischer , M. Godefroid

The potential energy curve of the F$_2$ molecule is calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC) using Configuration Interaction (CI)-type trial wavefunctions. To keep the number of determinants reasonable (the first and second…

Chemical Physics · Physics 2016-07-25 Emmanuel Giner , Anthony Scemama , Michel Caffarel

The multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) methods are used to provide excitation energies, radiative transition data, lifetimes, Lande g-factors, hyperfine interaction constants and…

Weighting methods are essential tools for estimating causal effects in observational studies, with the goal of balancing pre-treatment covariates across treatment groups. Traditional approaches pursue this objective indirectly, for example,…

Methodology · Statistics 2026-02-09 Diptanil Santra , Guanhua Chen , Chan Park

Truncated densities are probability density functions defined on truncated domains. They share the same parametric form with their non-truncated counterparts up to a normalizing constant. Since the computation of their normalizing constants…

Machine Learning · Statistics 2022-04-21 Song Liu , Takafumi Kanamori , Daniel J. Williams

Full Waveform Inversion (FWI) is a promising technique for achieving high-resolution imaging in medical ultrasound. However, conventional FWI methods suffer from issues related to computational efficiency, dependence on initial models, and…

Medical Physics · Physics 2025-10-15 Qiang Li , Heyu Ma , Chengcheng Liu , Dean Ta

Functional connectivity (FC) refers to the investigation of interactions between brain regions to understand integration of neural activity in several regions. FC is often estimated using functional magnetic resonance images (fMRI). There…

Applications · Statistics 2023-01-24 Nathan Tung , Jerome Sanes , Eli Upfal , Ani Eloyan

Analytic energy gradients are presented for a variational two-electron reduced-density-matrix-driven complete active space self-consistent field (v2RDM-CASSCF) procedure that employs the density-fitting (DF) approximation to the…

Chemical Physics · Physics 2018-11-29 J. Wayne Mullinax , Evgeny Epifanovsky , Gergely Gidofalvi , A. Eugene DePrince

In this study, we have calculated single-electron energy spectra via the Green's function based on the coupled-cluster singles and doubles (GFCCSD) method for isolated atoms from H to Ne. In order to check the accuracy of the GFCCSD method,…

Materials Science · Physics 2018-07-26 Hirofumi Nishi , Taichi Kosugi , Yoritaka Furukawa , Yu-ichiro Matsushita

We present the Copupled Cluster (CC) method and the Density matrix Renormalization Grooup (DMRG) method in a unified way, from the perspective of recent developments in tensor product approximation. We present an introduction into recently…

Chemical Physics · Physics 2017-11-22 Örs Legeza , Thorsten Rohwedder , Reinhold Schneider , Szilárd Szalay

We present a procedure to construct a configuration-interaction expansion containing arbitrary excitations from an underlying full-configuration-interaction-type wave function defined for a very large active space. Our procedure is based on…

Chemical Physics · Physics 2011-06-14 Katharina Boguslawski , Konrad H. Marti , Markus Reiher

We derive an expansion of the functional renormalization (fRG) equations that treats the frequency and momentum dependencies of the vertices in a systematic manner. The scheme extends the channel-decomposed fRG equations to the frequency…

Strongly Correlated Electrons · Physics 2021-07-07 Nahom K. Yirga , David K. Campbell

Fermi Normal Coordinates (FNC) are a useful frame for isolating the locally observable, physical effects of a long-wavelength spacetime perturbation. Their cosmological application, however, is hampered by the fact that they are only valid…

General Relativity and Quantum Cosmology · Physics 2015-12-02 Liang Dai , Enrico Pajer , Fabian Schmidt