SciPost Physics

SciPost Phys. 13, 078 (2022) · published 3 October 2022

• doi: 10.21468/SciPostPhys.13.4.078
• pdf
• BiBTeX
• RIS
• Submissions/Reports
• 

Abstract

The effective dynamics of a colloidal particle immersed in a complex medium is often described in terms of an overdamped linear Langevin equation for its velocity with a memory kernel which determines the effective (time-dependent) friction and the correlations of fluctuations. Recently, it has been shown in experiments and numerical simulations that this memory may depend on the possible optical confinement the particle is subject to, suggesting that this description does not capture faithfully the actual dynamics of the colloid, even at equilibrium. Here, we propose a different approach in which we model the medium as a Gaussian field linearly coupled to the colloid. The resulting effective evolution equation of the colloidal particle features a non-linear memory term which extends previous models and which explains qualitatively the experimental and numerical evidence in the presence of confinement. This non-linear term is related to the correlations of the effective noise via a novel fluctuation-dissipation relation which we derive.

• Caspers et al., How are mobility and friction related in viscoelastic fluids?
  158, 024901 (2023) [Crossref]
• Krishna Kumar et al., Memory-induced alignment of colloidal dumbbells
  Sci Rep 13, 17409 (2023) [Crossref]
• Venturelli et al., Memory-induced oscillations of a driven particle in a dissipative correlated medium
  New J. Phys. 25, 093025 (2023) [Crossref]
• Venturelli et al., Stochastic thermodynamics of a probe in a fluctuating correlated field
  EPL 146, 27001 (2024) [Crossref]
• Venturelli et al., Tracer particle in a confined correlated medium: an adiabatic elimination method
  J. Stat. Mech. 2022, 123210 (2022) [Crossref]
• Démery et al., Non-Gaussian fluctuations of a probe coupled to a Gaussian field
  Phys. Rev. E 108, 044604 (2023) [Crossref]
• Benois et al., Enhanced diffusion of tracer particles in nonreciprocal mixtures
  Phys. Rev. E 108, 054606 (2023) [Crossref]
• Gambassi et al., Critical Casimir forces in soft matter
  Soft Matter 20, 3212 (2024) [Crossref]
• Venturelli et al., Inducing oscillations of trapped particles in a near-critical Gaussian field
  Phys. Rev. E 106, 044112 (2022) [Crossref]