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We evaluate the two-point functions of the electromagnetic field in (D+1) -dimensional spatially flat Friedmann-Robertson-Walker universes with a power-law scale factor, assuming that the field is prepared in the Bunch-Davies vacuum state.…

High Energy Physics - Theory · Physics 2013-11-15 S. Bellucci , A. A. Saharian

We present a conjugate-gradient method for the ground-state optimization of projected entangled-pair states (PEPS) in the thermodynamic limit, as a direct implementation of the variational principle within the PEPS manifold. Our…

Strongly Correlated Electrons · Physics 2016-11-08 Laurens Vanderstraeten , Jutho Haegeman , Philippe Corboz , Frank Verstraete

We present two efficient and intruder-free methods for treating dynamic correlation on top of general multi-configuration reference wave functions---including such as obtained by the density matrix renormalization group (DMRG) with large…

Chemical Physics · Physics 2016-09-13 Sandeep Sharma , Gerald Knizia , Sheng Guo , Ali Alavi

Ensemble density functional theory (eDFT) is an exact time-independent alternative to time-dependent DFT (TD-DFT) for the calculation of excitation energies. Despite its formal simplicity and advantages in contrast to TD-DFT (multiple…

Strongly Correlated Electrons · Physics 2017-01-19 Killian Deur , Laurent Mazouin , Emmanuel Fromager

We present and compare several many-body methods as applied to two-dimensional quantum dots with circular symmetry. We calculate the approximate ground state energy using a harmonic oscillator basis optimized by Hartree-Fock (HF) theory and…

Double excitations are crucial to understanding numerous chemical, physical, and biological processes, but accurately predicting them remains a challenge. In this work, we explore the particle-particle random phase approximation (ppRPA) as…

Chemical Physics · Physics 2024-11-26 Jincheng Yu , Jiachen Li , Tianyu Zhu , Weitao Yang

Traditional finite-temperature Kohn-Sham density functional theory (KSDFT) has an unfavorable scaling with respect to the electron number or at high temperatures. The evaluation of the ground-state density in KSDFT can be replaced by the…

Computational Physics · Physics 2022-10-05 Qianrui Liu , Mohan Chen

We study mixed finite element methods for the linearized rotating shallow water equations with linear drag and forcing terms. By means of a strong energy estimate for an equivalent second-order formulation for the linearized momentum, we…

Numerical Analysis · Mathematics 2014-10-02 Colin J. Cotter , Robert C. Kirby

We present a new method, ePT, for extrapolating few known coefficients of a perturbative expansion. Controlled by comparisons with numerically exact quantum Monte Carlo (QMC) results, 10th order strong-coupling perturbation theory (PT) for…

Strongly Correlated Electrons · Physics 2007-05-23 N. Blümer , E. Kalinowski

Tailored optical excitations can steer a system along non-equilibrium pathways to metastable states with specific structural or electronic properties. The light-induced hidden state of 1T-TaS$_{2}$, with its strongly enhanced conductivity…

Van der Waals heterostructures of two-dimensional transition metal dichalcogenides provide a unique platform to engineer optoelectronic devices tuning their optical properties via stacking, twisting, or straining. Using ab initio Many-Body…

Mesoscale and Nanoscale Physics · Physics 2025-03-21 R. Reho , A. R. Botello-Méndez , D. Sangalli , M. J. Verstraete , Zeila Zanolli

A previously proposed non-canonical coupled-perturbed Kohn-Sham density functional theory (KS-DFT)/Hartree-Fock (HF) treatment for spin-orbit coupling is here generalized to infinite periodic systems. The scalar-relativistic periodic…

We explore the use of optimized operators, designed to interpolate only a single meson eigenstate, in three-point correlation functions with a vector-current insertion. These operators are constructed as linear combinations in a large basis…

High Energy Physics - Lattice · Physics 2015-01-30 Christian J. Shultz , Jozef J. Dudek , Robert G. Edwards

We present a modification of the $\Delta$SCF method of calculating energies of excited states, in order to make it applicable to resonance calculations of molecules adsorbed on metal surfaces, where the molecular orbitals are highly…

Materials Science · Physics 2009-03-06 Jeppe Gavnholt , Thomas Olsen , Mads Engelund , Jakob Schiøtz

A new version release (2.0) of the molecular simulation tool ms2 [S. Deublein et al., Comput. Phys. Commun. 182 (2011) 2350] is presented. Version 2.0 of ms2 features a hybrid parallelization based on MPI and OpenMP for molecular dynamics…

We develop a multipoint stress mixed finite element method for linear elasticity with weak stress symmetry on quadrilateral grids, which can be reduced to a symmetric and positive definite cell centered system. The method is developed on…

Numerical Analysis · Mathematics 2019-08-06 Ilona Ambartsumyan , Eldar Khattatov , Jan M. Nordbotten , Ivan Yotov

The Effective Field Theory of Large-Scale Structure (EFTofLSS) attempts to amend some of the shortcomings of the traditional perturbative methods used in cosmology. It models the evolution of long-wavelength perturbations above a cutoff…

Cosmology and Nongalactic Astrophysics · Physics 2024-08-15 Mandar Karandikar , Cristiano Porciani , Oliver Hahn

Infinite projected entangled-pair states (iPEPS) provide a powerful tensor network ansatz for two-dimensional quantum many-body systems in the thermodynamic limit. In this paper we introduce an approach to accurately compute the energy…

Strongly Correlated Electrons · Physics 2025-12-01 Emilio Cortés Estay , Naushad A. Kamar , Philippe Corboz

We present a detailed comparison of the S0, S1 (n -> \pi*) and S2 (\pi -> \pi*) potential energy surfaces (PESs) of the prototypical molecular switch azobenzene as obtained by Delta-self-consistent-field (Delta-SCF) Density-Functional…

Chemical Physics · Physics 2012-02-22 Reinhard J. Maurer , Karsten Reuter

We introduce and study a variational framework for the analysis of empirical risk based inference for dynamical systems and ergodic processes. The analysis applies to a two-stage estimation procedure in which (i) the trajectory of an…

Dynamical Systems · Mathematics 2018-01-24 Kevin McGoff , Andrew B. Nobel