Spatial multi-level interacting particle simulations and information theory-based error quantification

TL;DR

This paper introduces a multi-level kinetic Monte Carlo framework for efficient sampling of complex high-dimensional stochastic lattice systems, with error quantification based on information theory, applicable to long-time dynamics and metastability analysis.

Contribution

It develops a novel multi-level algorithm combining coarse-graining and microscopic reconstruction, with rigorous error analysis and adaptability for long-time and stationary regime simulations.

Findings

Error grows linearly with time in the multi-level method

Information loss can be estimated or tracked during simulations

The method unifies rejection-free and null-event algorithms

Abstract

We propose a hierarchy of multi-level kinetic Monte Carlo methods for sampling high-dimensional, stochastic lattice particle dynamics with complex interactions. The method is based on the efficient coupling of different spatial resolution levels, taking advantage of the low sampling cost in a coarse space and by developing local reconstruction strategies from coarse-grained dynamics. Microscopic reconstruction corrects possibly significant errors introduced through coarse-graining, leading to the controlled-error approximation of the sampled stochastic process. In this manner, the proposed multi-level algorithm overcomes known shortcomings of coarse-graining of particle systems with complex interactions such as combined long and short-range particle interactions and/or complex lattice geometries. Specifically, we provide error analysis for the approximation of long-time stationary dynamics in terms of relative entropy and prove that information loss in the multi-level methods is growing linearly in time, which in turn implies that an appropriate observable in the stationary regime is the information loss of the path measures per unit time. We show that this observable can be either estimated a priori, or it can be tracked computationally a posteriori in the course of a simulation. The stationary regime is of critical importance to molecular simulations as it is relevant to long-time sampling, obtaining phase diagrams and in studying metastability properties of high-dimensional complex systems. Finally, the multi-level nature of the method provides flexibility in combining rejection-free and null-event implementations, generating a hierarchy of algorithms with an adjustable number of rejections that includes well-known rejection-free and null-event algorithms.