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We present a symmetry-adapted perturbation theory (SAPT) for the interaction of two high-spin open-shell molecules (described by their restricted open-shell Hartree-Fock determinants) resulting in low-spin states of the complex. The…

Chemical Physics · Physics 2018-05-23 Konrad Patkowski , Piotr S. Żuchowski , Daniel G. A. Smith

Methods for calculating lower bounds to the exact energy using the variance of the upper bound energy are discussed and explored. All the matrix elements of the Hamiltonian squared are collected and considered, and those for which no known…

Quantum Physics · Physics 2021-07-09 Robbie Thomson Ireland

The well-known spatial integration schemes in molecular electronic structure theory, immune to cusps and point singularities of some kind at atomic positions, use a set of weighting functions to split the integrand into a sum of…

Chemical Physics · Physics 2022-09-14 Dimitri N. Laikov

Situations of a functional predictor paired with a scalar response are increasingly encountered in data analysis. Predictors are often appropriately modeled as square integrable smooth random functions. Imposing minimal assumptions on the…

Statistics Theory · Mathematics 2009-09-08 Peter Hall , Hans-Georg Müller , Fang Yao

This paper derives and demonstrates a new, purely density-based ab initio approach for calculation of the energies and properties of many-electron systems. It is based upon the discovery of relationships that govern the "mechanics" of the…

Chemical Physics · Physics 2024-09-04 James C. Ellenbogen

We aim at deriving an equation of motion for specific sums of momentum mode occupation numbers from models for electrons in periodic lattices experiencing elastic scattering, electron-phonon scattering or electron-electron scattering. These…

Quantum Gases · Physics 2010-05-18 Christian Bartsch , Robin Steinigeweg , Jochen Gemmer

We analyze the classical equations of motion for a particle moving in the presence of a static magnetic field applied in the $ z $ direction, which varies as $ {1\over{x^2}} $. We find the symmetries through Lie's method of group analysis.…

Mathematical Physics · Physics 2007-05-23 Karmadeva Maharana

We present a derivation of the gradients of feedforward neural networks using Fr\'echet calculus which is arguably more compact than the ones usually presented in the literature. We first derive the gradients for ordinary neural networks…

Machine Learning · Computer Science 2022-09-28 Thomas Hamm

A consequent approach is proposed to construct symplectic force-gradient algorithms of arbitrarily high orders in the time step for precise integration of motion in classical and quantum mechanics simulations. Within this approach the basic…

Statistical Mechanics · Physics 2009-11-07 Igor Omelyan , Ihor Mryglod , Reinhard Folk

The observation and description of collective excitations in solids is a fundamental issue when seeking to understand the physics of a many-body system. Analysis of these excitations is usually carried out by measuring the dynamical…

Based on the Korringa-Kohn-Rostoker Green's function technique we present a computational scheme for calculating the electronic structure of layered systems with homogeneous spin-spiral magnetic state. From the self-consistent…

Materials Science · Physics 2019-10-30 Eszter Simon , Laszlo Szunyogh

A non-linear conjugate gradient optimization scheme is used to obtain excitation energies within the Random Phase Approximation (RPA). The solutions to the RPA eigenvalue equation are located through a variational characterization using a…

Materials Science · Physics 2011-11-21 Melissa J. Lucero , Anders M. N. Niklasson , Sergei Tretiak , Matt Challacombe

In the simulation of biological molecules, it is customary to impose constraints on the fastest degrees of freedom to increase the time step. The evaluation of the involved constraint forces must be performed in an efficient manner, for…

Computational Physics · Physics 2019-11-01 Pablo García-Risueño

We present some results and remarks based on a combinatorial approach of the evaluation of the nuclear level density. First, we show that it is possible to extract some reliable information from the output of the program whose rough data…

Nuclear Theory · Physics 2007-05-23 Bernard PICHON CNRS

We derive a set of equations expressing the parameters of the magnetic interactions characterizing a strongly correlated electronic system in terms of single-electron Green's functions and self-energies. This allows to establish a mapping…

Strongly Correlated Electrons · Physics 2016-01-20 Andrea Secchi , Alexander I. Lichtenstein , Mikhail I. Katsnelson

The wavefunction for the multiparticle Schr\"odinger equation is a function of many variables and satisfies an antisymmetry condition, so it is natural to approximate it as a sum of Slater determinants. Many current methods do so, but they…

Mathematical Physics · Physics 2009-11-13 Gregory Beylkin , Martin J. Mohlenkamp , Fernando Pérez

We study a simple analytic solution to Einstein's field equations describing a thin spherical shell consisting of collisionless particles in circular orbit. We then apply two independent criteria for the identification of circular orbits,…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Monica L. Skoge , Thomas W. Baumgarte

In arXiv:1707.06803 we derived the subleading multiple soft graviton theorem in a generic quantum theory of gravity for arbitrary number of soft external gravitons and arbitrary number of finite energy external states carrying arbitrary…

High Energy Physics - Theory · Physics 2018-02-14 Subhroneel Chakrabarti , Sitender Pratap Kashyap , Biswajit Sahoo , Ashoke Sen , Mritunjay Verma

A parallel implementation of coupled spin-lattice dynamics in the LAMMPS molecular dynamics package is presented. The equations of motion for both spin only and coupled spin-lattice dynamics are first reviewed, including a detailed account…

Statistical Mechanics · Physics 2018-08-01 J. Tranchida , S. J. Plimpton , P. Thibaudeau , A. P. Thompson

The aggregation equation arises naturally in kinetic theory in the study of granular media, and its interpretation as a 2-Wasserstein gradient flow for the nonlocal interaction energy is well-known. Starting from the spatially homogeneous…

Analysis of PDEs · Mathematics 2024-12-24 A. Esposito , R. S. Gvalani , A. Schlichting , M. Schmidtchen