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We extend the phase field crystal model to accommodate exact atomic configurations and vacancies by requiring the order parameter to be non-negative. The resulting theory dictates the number of atoms and describes the motion of each of…

Computational Physics · Physics 2009-02-10 Pak Yuen Chan , Nigel Goldenfeld , Jon Dantzig

Accurately modeling chemical reactions at the atomistic level requires high-level electronic structure theory due to the presence of unpaired electrons and the need to properly describe bond breaking and making energetics. Commonly used…

We study two different physical scenarios of thermonuclear reactions in stellar plasmas proceeding through a narrow resonance at low energy or through the low energy wing of a wide resonance at high energy. Correspondingly, we derive two…

Nuclear Theory · Physics 2009-11-10 F. Ferro , A. Lavagno , P. Quarati

Reactive flows are important part of numerous technical and environmental processes. Often monitoring the flow and species concentrations within the domain is not possible or is expensive, in contrast, outlet concentration is…

Fluid Dynamics · Physics 2022-04-26 Daria Fokina , Oleg Iliev , Pavel Toktaliev , Ivan Oseledets , Felix Schindler

Reaction-diffusion models have been used over decades to study biological systems. In this context, evolution equations for probability distribution functions and the associated stochastic differential equations have nowadays become…

Statistical Mechanics · Physics 2018-10-09 C. Escudero , S. B. Yuste , E. Abad , F. Le Vot

To stabilize the periodic operation of a chemical reactor the oscillation period should be determined precisely in real time. The method discussed in the paper is based on adaptive sampling of the state variable with the use of chaotic…

Chaotic Dynamics · Physics 2026-02-10 Marcin Lawnik , Marek Berezowski

We present a kinetic Monte Carlo method for simulating chemical transformations specified by reaction rules, which can be viewed as generators of chemical reactions, or equivalently, definitions of reaction classes. A rule identifies the…

Quantitative Methods · Quantitative Biology 2010-07-09 Jin Yang , Michael I. Monine , James R. Faeder , William S. Hlavacek

We provide a dynamical interpretation of the recently identified `roaming' mechanism for molecular dissociation reactions in terms of geometrical structures in phase space. These are NHIMs (Normally Hyperbolic Invariant Manifolds) and their…

In this work, we investigate the existence of transition state resonances on atom-diatom reactive collisions from a time-dependent perspective, stressing the role of quantum trajectories as a tool to analyze this phenomenon. As it is shown,…

Chemical Physics · Physics 2012-05-25 A. S. Sanz , D. Lopez-Duran , T. Gonzalez-Lezana

A new alternate method for evaluating linear response theory is formally developed, and results are presented. This method involves the time-evolution of the system using TDHF and is constructed directly on top of a static Hartree-Fock…

Nuclear Theory · Physics 2009-11-11 A. S. Umar , V. E. Oberacker

We introduce a rigorous method to microscopically compute the observables which characterize the thermodynamics and kinetics of rare macromolecular transitions for which it is possible to identify a priori a slow reaction coordinate. In…

Biomolecules · Quantitative Biology 2015-06-05 P. Faccioli , F. Pederiva

We introduce a nonlinear stochastic model reduction technique for high-dimensional stochastic dynamical systems that have a low-dimensional invariant effective manifold with slow dynamics, and high-dimensional, large fast modes. Given only…

Machine Learning · Statistics 2023-10-25 Felix X. -F. Ye , Sichen Yang , Mauro Maggioni

If a given behavior of a multi-agent system restricts the phase variable to a invariant manifold, then we define a phase transition as change of physical characteristics such as speed, coordination, and structure. We define such a phase…

Dynamical Systems · Mathematics 2017-07-21 Kelum Gajamannage , Erik M. Bollt

The low-temperature driven or thermally activated motion of several condensed matter systems is often modeled by the dynamics of interfaces (co-dimension-1 elastic manifolds) subject to a random potential. Two characteristic quantitative…

Disordered Systems and Neural Networks · Physics 2009-10-31 A. Alan Middleton

The modelling of linear and nonlinear reaction-subdiffusion processes is more subtle than normal diffusion and causes different phenomena. The resulting equations feature a spatial Laplacian with a temporal memory term through a time…

Analysis of PDEs · Mathematics 2021-08-24 Jichen Yang , Jens D. M. Rademacher

A thorough analysis is performed to find traveling waves in a qualitative reaction-diffusion system inspired by a predator-prey model. We provide rigorous results coming from a standard local stability analysis, numerical bifurcation…

Chaotic Dynamics · Physics 2022-11-09 Edgardo Villar-Sepúlveda , Pablo Aguirre , Víctor F. Breña-Medina

A new upscaling procedure that provides 1D representations of 2D mixing-limited reactive transport systems is developed and applied. A key complication with upscaled models in this setting is that the procedure must differentiate between…

Fluid Dynamics · Physics 2022-10-05 Ricardo H. Deucher , Louis J. Durlofsky

We present a general model allowing one to calculate the distribution function of energetic particles in the interstellar medium, and hence any relevant nuclear reaction rate, for any given time-dependent injection function, as well as in…

Astrophysics · Physics 2007-05-23 Etienne Parizot

Calculating fusion reactivity involves a complex six-dimensional integral of the fusion cross section and ion velocity distributions of two reactants. We demonstrate a simple Monte Carlo approach that efficiently computes this integral for…

Computational Physics · Physics 2023-08-02 Huasheng Xie

During reactive transport modeling, the computational cost associated with chemical reaction calculations is often 10-100 times higher than that of transport calculations. Most of these costs results from chemical equilibrium calculations…

Optimization and Control · Mathematics 2017-08-17 Allan M. M. Leal , Dmitrii A. Kulik , Martin O. Saar
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