Collective Behaviors

Independently moving micro-swimmer shows interesting collective behavior. As these micro-swimmers propel themselves, they are often called self-propelled swimmers. The collective motions of the self-propelled swimmers are commonly observed in flocks of birds, school of fish, human crowds, bacterial colonies, different cells etc. The behavior of the micro-swimmers largely differs when they are placed in confined spaces rather than moving freely. In our group, we are interested to model the behavior of the micro-swimmers in the confined domain. The problems we are mainly working on (a) collective motion of the swimmers in a confined domain, (b) mixing/ segrigation of the micro-swimmers (c) behavior of the micro-swimmers in presence of a predator.

Dynamics of active matter:

Active matter models involve particles that are able to propel by virtue of their internal energy. These particles are assumed to be indicative of organisms such as bacteria. The physics of a system of self-propelling particles in the presence of competing forces of alignment and repulsion is examined. Formation of novel spatial patterns such as ring-shaped mills and hybrid mills-clusters is observed. Dynamical analysis carried out through the study of chaos and synchronisation in the system shows the formation of weak chimera composite among the particles. A new state of weak chimera coined as ‘multi-band weak chimera’ with multiple synchronised oscillator groups is also detected. This study serves as an ideal case study for the DEM-based model used for the simulation of active dry matter.

Two species antagonistic interaction model:

Collective behaviour might occur due to a plethora of reasons such as the presence of danger or need for foraging or reduction in energy consumption or facilitating smooth movement in a crowded environment. Among these situations, the majority of animals portray self-organisation when subjected to predation. Especially in the case of fish, a rich variety of pattern formation is observed, such as mill, ball, fountain, split, and more. The physics underlying the collective behaviour in the presence of a predator is studied in the purview of self-propelling particles inside a confined domain. A novel force-based Vicsek model is utilised to simulate the interactions among the particles. It is observed that the information about the presence of the predator is passed from the afflicted prey to its neighbours, which then pass it onto their neighbours and so on. The signal intensity, however, is found to be diminishing with distance, which, in other words, means that there is a localisation of transfer of information. This study lays the groundwork for the development of a model that is able to simulate the interactions between a pathogen and healthy cells or between a drug molecule and the diseased cells.

For details see:

  1. Siddhant Mohapatra, Sirshendu Mondal, and Pallab Sinha Mahapatra, Spatiotemporal dynamics of a self-propelled system with opposing alignment and repulsive forces, Physical Review E, (2020), 102, 042613.
  2. Naveen Kumar Agrawal and Pallab Sinha Mahapatra, Effect of particle fraction on phase transitions in an active-passive particles system, Physical Review E, (2020) 101, 042607.
  3. Siddhant Mohapatra and Pallab Sinha Mahapatra, Confined System Analysis of a Predator-Prey Minimalistic Model, Nature Scientific Reports, (2019) 9, 11258 PDF.
  4. Pallab Sinha Mahapatra and Sam Mathew, Activity induced mixing and phase transitions of self-propelled swimmers, Physical Review E, (2019) 99, 012609.
  5. Pallab Sinha Mahapatra, Ajinkya Kulkarni, Sam Mathew, Mahesh V. Panchagnula, and Srikanth Vedantam, Transitions between multiple dynamical states in a confined dense active-particle system, Physical Review E, (2017) 95, 062610.