Linear control theory for jammed particle systems

TL;DR

This paper applies linear control theory to jammed particle systems, revealing how controllability metrics predict particle rearrangements and offering new insights into the dynamics of disordered materials under stress.

Contribution

It introduces linear control theory tools to analyze jammed amorphous materials, linking controllability measures to particle rearrangements and optimizing predictive time scales.

Findings

Average controllability correlates with particle rearrangement.

Optimal time scale enhances prediction of rearrangements.

Lower energy vibrational modes involve more particles during rearrangement.

Abstract

Amorphous particulate matter constitutes a wide range of natural and synthetic materials. Despite this ubiquity, the way in which these systems' disordered microstructure couples to their often subtle and complex dynamical behavior is not yet fully understood, with profound consequences for phenomena ranging from landscape evolution to cellular unjamming during tumor metastasis. With this paper, we introduce tools from linear control theory that quantify system response to external input, and demonstrate their utility in elucidating the dynamics of jammed amorphous materials under stress. Our results indicate that average controllability, the response of a system to perturbation, strongly correlates with particle rearrangement in systems subject to quasistatic shear, implying that average controllability is an accurate predictor of rearrangement dynamics in certain contexts. Moreover, we show that the time scale over which average controllability is calculated can be tuned to optimize its predictive capacity for particle rearrangement. Values of the optimal time scale provide physical insight into the system; namely, that multiple rearranging particles participate on average in vibrational eigenmodes of lower and lower energy as the system is sheared until the rearrangement event. Broadly, our study demonstrates that linear control theory is a promising mathematical framework for predicting and designing mechanical response in disordered media.