Dynamics of a colloidal particle coupled to a Gaussian field: From a confinement-dependent to a non-linear memory

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.

(Abstract)

SCIPOST PHYSICS
Volume 13 / Issue 4 / Article Number 078
Published OCT 2022

DOI10.21468/SciPostPhys.13.4.078

By: Urna Basu, Vincent Démery, Andrea Gambassi


Top



See also...

Harnessing DNA computing and nanopore decoding for practical applications: from informatics to microRNA-targeting diagnostics

DNA computing represents a subfield of molecular computing with the potential to become a significant area of next-generation computation due to (…) 

> More...

Microscopic foundation of the mu(I) rheology for dense granular flows on inclined planes

Macroscopic and microscopic properties of dense granular layers flowing down inclined planes are obtained from Discrete-Element-Method simulations (…) 

> More...