Theoretical Sciences Unit Seminar

Theoretical Sciences Unit Seminar

Date: 22nd November 2022 (Tuesday)

]Title: Unusual Properties of Athermal Persistent Active Matter

Speaker: Prof. Chandan Dasgupta

Affiliation: IISc and ICTS, Bangalore

Time: 02:00 PM  |  Tea/Coffee: 01:45 PM

Venue: Kanada Auditorium, JNCASR

Abstract

Active matter consists of objects that can convert internal or ambient sources of energy into systematic motion. In several biological systems, such as bacterial cytoplasm, cytoskeleton-motor complexes, and epithelial sheets of cells, self-propulsion or activity is found to fluidize states that exhibit characteristic glassy behavior and jamming in the absence of activity.

I will discuss some of the results of our recent studies of jamming in athermal models of dense active matter. These models characterize self-propulsion force by two parameters: its magnitude and the persistence time associated with the decorrelation of its direction. In the limit of infinite persistence time, a dense system of athermal active particles exhibits a jamming transition as the strength of the active force decreases. The jammed state obtained for small active forces differs substantially from passive jammed systems.

I will present the results of numerical studies on the properties of active jammed states and a scaling description of these properties. The homogeneous liquid state obtained at large values of the active force also exhibits unusual properties: the average kinetic energy and the width of the distribution of kinetic energy increase with system size. A length scale extracted from spatial velocity correlations grows with system size without showing any sign of saturation.

We also investigate how this active liquid transitions into a force-balanced jammed state when the self-propulsion force is removed or reduced to a small value. The jamming occurs via a three-stage relaxation process whose timescale grows with the magnitude of the active force and system size. The dependence on system size is linked to the large correlation length observed in the liquid state.

All are cordially invited.