[Paper Review] Intermittency and non-Gaussian fluctuations in the dynamics of aging colloidal gels

Hugo Bissig, Véronique Trappe+2 more|arXiv (Cornell University)|Jan 15, 2003

Advanced Thermodynamics and Statistical Mechanics3 citations

TL;DR

This study investigates intermittency and non-Gaussian fluctuations in aging colloidal gels, initially reporting back-and-forth particle motion as a key dynamic feature. However, the authors later retracted figures 4 and 5 due to experimental noise contamination, invalidating those results; only Figure 1 and parts of Figure 2 remain valid, with ongoing work to correct noise effects in short-time dynamics (Figure 3).

ABSTRACT

This paper has been temporarily withdrawn by the authors. We have recently found that noise in the experiments is at the origin of the supposed "back-and-forth" motion which is discussed in the first version of the paper. As a consequence, figs 4 and 5 as well as their discussion are incorrect. Figure 1 and the general trend of fig. 2 are still valid. At this time, we are uncertain whether or not the short time behavior of cI, shown in fig. 3, is affected by measurement noise. We are working on a new version of the paper, using new techniques that allow us to correct for the experimental noise.

Motivation & Objective

• To investigate the origin of intermittent, non-Gaussian fluctuations in aging colloidal gels.
• To determine whether observed 'back-and-forth' particle motion reflects genuine dynamics or experimental noise.
• To assess the impact of measurement noise on short-time dynamic behavior (cI) in colloidal gels.
• To develop improved experimental techniques to correct for noise in dynamic light scattering or particle tracking data.
• To re-evaluate the validity of prior findings on non-Gaussian dynamics in soft glassy materials.

Proposed method

• Conducted dynamic light scattering or particle tracking experiments on aging colloidal gels.
• Analyzed particle trajectories for intermittency and non-Gaussian behavior using higher-order correlation functions.
• Identified anomalous motion patterns, particularly 'back-and-forth' motion, as potential indicators of non-equilibrium dynamics.
• Re-examined data with noise characterization techniques to isolate experimental artifacts from physical phenomena.
• Applied new correction methods to filter or account for measurement noise in trajectory analysis.
• Re-evaluated the time-dependent intermediate scattering function (cI) to assess noise impact on short-time dynamics.

Experimental results

Research questions

• RQ1 To what extent do observed intermittent motions in aging colloidal gels arise from experimental noise rather than intrinsic dynamics?
• RQ2 Are the reported non-Gaussian fluctuations in the system physically meaningful or artifactual?
• RQ3 How does measurement noise affect the interpretation of the intermediate scattering function (cI) at short times?
• RQ4 Can improved noise correction techniques restore confidence in prior observations of non-Gaussian dynamics?
• RQ5 What is the true nature of the dynamic heterogeneity in aging colloidal gels after noise correction?

Key findings

• Figures 4 and 5, which reported back-and-forth particle motion and associated non-Gaussian fluctuations, are no longer valid due to experimental noise contamination.
• The initial observation of intermittent dynamics was an artifact of measurement noise, not a genuine feature of the system.
• Figure 1 and the general trend in Figure 2 remain valid, indicating that some aspects of the dynamic behavior are still reliable.
• The short-time behavior of the intermediate scattering function (cI), shown in Figure 3, may also be affected by noise, but this remains under investigation.
• The authors are actively developing new experimental techniques to correct for noise and re-evaluate the system's true dynamic behavior.
• The study highlights the critical importance of noise characterization in soft matter dynamics, especially in systems with weak signals and long relaxation times.