Speaker
Description
We study the collective dynamics for a viscoelastic active system where the fluctuation-dissipation theorem (FDT) is violated. We set up a minimal model, where an active Brownian particle (ABP) is cross-linked to a star polymer of functionality f in a viscous fluid. The ABP has self-propelled motion from its own energy consumption and attains a strong non-Markovian anomalous motion due to the viscoelastic feedback from the polymer. We have performed extensive Langevin dynamics simulations on this system at various conditions for two cases in which a star polymer is made up with Rouse chains or worm-like chains (WLC). Our study shows that in the Rouse polymer system the ABP cross-linker with the scaling $\langle\Delta R^2(t)\rangle\sim t^{\alpha}$ has rich dynamic patterns from the Rouse dynamics ($\sim t^{1/2}$) to logarithmic one ($\sim \ln t$) depending on the strength of self-propulsion[1]. In the WLC environment, the ABP cross-linker shows distinct dynamic behavior. In particular, the seemingly Rouse dynamics can occur due to the active non-equilibrium fluctuation. We explain the observed collective dynamics of the ABP cross-linker in the framework of generalized Langevin equations with two distinct--thermal and athermal--noises.
[1] S. Joo, X. Durang, O.-c. Lee, and J.-H. Jeon, Soft Matter 16, 9188–9201 (2020)
