Spatiotemporal Dynamics: Insights into Dense Active Matter

with Dr. Amir Shee (University of Vermont)

Dense active matter, composed of self-propelled particles packed closely together, reveals fascinating and often unexpected behaviors in both space and time. These behaviors illustrate how simple individual units can generate complex dynamics. Such systems include a wide range of natural and artificial examples, from bacterial colonies and epithelial tissues to vibrated granular matter, robotic swarms, artificial swimmers, human crowds, and animal herds.

In this talk, I will highlight our recent analytic and computational advances in dense active matter research. First, I will introduce a new generic model that exhibits a novel noise-induced quenched disorder (QD) state, emerging between flocking and disorder states. In QD regime, self-propelled particles become jammed with random orientations, displaying only small fluctuations around their average positions and headings. I explain the emergence of this new state using a simple analytical hypothesis.

Next, I will focus on chiral dense active matter, where individual self-propelled particles rotate with a constant angular velocity. I will present the full phase diagram of this system exhibiting the emergence of mesoscale correlations utilizing analytic normal mode formulation and linear elasticity theory. These results demonstrate how noise and chirality can drive rich and varied collective dynamics in dense chiral active matter.

If time permits, I will present some of our recent results on the ongoing project exploring optimal unjamming behavior in dense active-passive mixtures.

References:

Noise-Induced Quenched Disorder in Dense Active Systems. Guozheng Lin, Zhangang Han, Amir Shee, and Cristián Huepe, Phys. Rev. Lett. 131, 168301 (2023)
Emergent mesoscale correlations in active solids with noisy chiral dynamics. Amir Shee, Silke Henkes, and Cristián Huepe, Soft Matter, 2024, 20, 7865-7879

Biography: Dr. Amir Shee is a theoretical physicist currently serving as a Postdoctoral Research Associate in Prof. Haicen Yue’s lab at the Department of Physics, UVM. He earned his Ph.D. from the Institute of Physics in Bhubaneswar, India, and subsequently held a postdoctoral position at Northwestern University before joining UVM.

Dr. Shee specializes in non-equilibrium statistical mechanics, with a particular focus on active matter, soft matter, and biophysics. His current research explores emergent rheology in advanced adaptive active matter models. His work integrates theoretical modeling, employing both analytical and computational approaches, with practical applications ranging from artificial to natural active systems.