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A collective description of density matrix is presented for identical multi-level atoms, which are either excited initially, driven coherently or pumped incoherently. The density matrix is defined as expectation value of projection or…

Quantum Physics · Physics 2019-12-17 Yuan Zhang

Comprehensive and confident identifications of metabolites and other chemicals in complex samples will revolutionize our understanding of the role these chemically diverse molecules play in biological systems. Despite recent advances,…

We develop an algorithm for bosonic path integral molecular dynamics (PIMD) simulations with periodic boundary conditions (PBC) that scales quadratically with the number of particles. Path integral methods are a powerful tool to simulate…

Chemical Physics · Physics 2025-09-16 Jacob Higer , Yotam M. Y. Feldman , Barak Hirshberg

Structurally and chemically complex materials such as amorphous metallosilicates underpin major catalytic and separation technologies, yet their intrinsic complexity challenges reliable atomistic modeling under realistic conditions.…

We present second-order molecular cluster perturbation theory (MCPT(2)), a linear scaling methodology to calculate arbitrarily large systems with explicit calculation of individual wavefunctions in a coupled-cluster framework. This new…

Accurate modelling of electrostatic interactions and charge transfer is fundamental to computational chemistry, yet most machine learning interatomic potentials (MLIPs) rely on local atomic descriptors that cannot capture long-range…

Semidefinite programs (SDPs) are a framework for exact or approximate optimization that have widespread application in quantum information theory. We introduce a new method for using reductions to construct integrality gaps for SDPs. These…

Quantum Physics · Physics 2019-03-18 Aram W. Harrow , Anand Natarajan , Xiaodi Wu

Symplectic N-body integrators are widely used to study problems in celestial mechanics. The most popular algorithms are of 2nd and 4th order, requiring 2 and 6 substeps per timestep, respectively. The number of substeps increases rapidly…

Astrophysics · Physics 2009-10-31 J. E. Chambers , M. A. Murison

A new method is proposed for integrating the equations of motion of an elastic filament. In the standard finite-difference and finite-element formulations the continuum equations of motion are discretized in space and time, but it is then…

Computational Physics · Physics 2009-11-13 Anthony JC Ladd , Gaurav Misra

Order parameters based on spherical harmonics and Fourier coefficients already play a significant role in condensed matter research in the context of systems of spherical or point particles. Here, we extend these types of order parameter to…

Soft Condensed Matter · Physics 2010-12-22 Aaron S. Keys , Christopher R. Iacovella , Sharon C. Glotzer

An extended Hamiltonian approach to conduct isothermal-isobaric molecular dynamics simulations with full cell flexibility is presented. The components of the metric tensor are used as the fictitious degrees of freedom for the cell, thus…

Chemical Physics · Physics 2009-11-07 E. Hernandez

In this paper the problem is posed of determining the physically-meaningful asymptotic orderings holding for the statistical description of a large $N-$body system of hard spheres,\textit{ i.e.,} formed by $N\equiv\frac{1}{\varepsilon}…

Classical Physics · Physics 2017-04-26 Massimo Tessarotto , Claudio Asci

The worldline path-integral method, developed thus far for scalar fields, offers promising computational efficiency in general geometries, However, it relies so far on the scalar approximation that decomposes electromagnetic waves into two…

Quantum Physics · Physics 2025-09-16 He Zheng , Daniel A. Steck

We present a simple and robust technique to extract kinetic rate models and thermodynamic quantities from single molecule time traces. SMACKS (Single Molecule Analysis of Complex Kinetic Sequences) is a maximum likelihood approach that…

Quantitative Methods · Quantitative Biology 2022-03-10 Sonja Schmid , Markus Götz , Thorsten Hugel

We introduce and explore an approach for constructing force fields for small molecules, which combines intuitive low body order empirical force field terms with the concepts of data driven statistical fits of recent machine learned…

Chemical Physics · Physics 2020-10-26 Alice Allen , Gábor Csányi , Geneviève Dusson , Christoph Ortner

Symmetries impose structure on the Hilbert space of a quantum mechanical model. The mathematical units of this structure are the irreducible representations of symmetry groups and I consider how they function as conceptual units of…

Quantum Physics · Physics 2018-01-29 N. L. Harshman

We construct a new type of S-matrix in quantum field theory using the general boundary formulation. In contrast to the usual S-matrix the space of free asymptotic states is located at spatial rather than at temporal infinity. Hence, the new…

High Energy Physics - Theory · Physics 2008-11-26 Daniele Colosi , Robert Oeckl

This paper provides a detailed account of the numerical implementation of the stochastic equation of motion (SEOM) method for the dissipative dynamics of fermionic open quantum systems. To enable direct stochastic calculations, a minimal…

Statistical Mechanics · Physics 2020-06-24 Arif Ullah , Lu Han , Yun-An Yan , Xiao Zheng , YiJing Yan , Vladimir Chernyak

We propose the -- to the best of our knowledge -- first fully functional implementation of the ``Separation by a Convex Body'' (SCB) approach first outlined in Grzybowski et al. [1] for classification, separating two data sets using an…

Optimization and Control · Mathematics 2025-09-01 Antonio Frangioni , Enrico Gorgone , Benedetto Manca

This paper is to build a primitive framework for a new possible extended system of real mathematical analysis - the Isomorphic Mathematical Analysis System (IMAS). It is based on some new concepts: e.g. isomorphic frame,…

General Mathematics · Mathematics 2024-01-30 Yuan Liu