This is an announcement for the Theoretical Sciences Unit's Seminar on 22nd November 2022 (Tuesday).
Title: Unusual Properties of Athermal Persistent Active Matter
Speaker: Prof. Chandan Dasgupta
Affiliation: IISc and ICTS, Bangalore
Date and Time: 22nd November 2022 (Tuesday).Time: 02:00 PM Tea/Coffee: 01:45 PM
Venue: Kanada Auditorium, JNCASR
Title: Unusual Properties of Athermal Persistent Active Matter
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 behaviour 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. In these models, the self-propulsion force is characterized by two parameters: its magnitude and the persistence time associated with the decorrelation of its direction. In our studies, we consider the limit of infinite persistence time. In this limit, dense system of athermal active particles exhibit a jamming transition as the strength of the active force is decreased. The properties of the jammed state obtained for small active force are substantially different from those of passive jammed systems. I will present the results of numerical studies of 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 the kinetic energy increase with increasing system size and a length scale extracted from spatial velocity correlations increases with system size without showing any sign of saturation. We also investigate how this active liquid approaches a force-balanced jammed state when the self-propulsion force is removed or reduced to a small value. The jamming proceeds via a three-stage relaxation process whose timescale grows with the magnitude of the active force and the system size. We relate the dependence on the system size to the large correlation length observed in the liquid state.
