Banerjee Jyoti Prasad, Mandal Rituparno, Banerjee Deb Sankar, Thutupalli Shashi, Rao Madan
Simons Centre for the Study of Living Machines, National Centre for Biological Sciences (TIFR), Bangalore, India.
Institute for Theoretical Physics, Georg-August-Universität Göttingen, 37077, Göttingen, Germany.
Nat Commun. 2022 Aug 4;13(1):4533. doi: 10.1038/s41467-022-31984-z.
A dilute suspension of active Brownian particles in a dense compressible viscoelastic fluid, forms a natural setting to study the emergence of nonreciprocity during a dynamical phase transition. At these densities, the transport of active particles is strongly influenced by the passive medium and shows a dynamical jamming transition as a function of activity and medium density. In the process, the compressible medium is actively churned up - for low activity, the active particle gets self-trapped in a cavity of its own making, while for large activity, the active particle ploughs through the medium, either accompanied by a moving anisotropic wake, or leaving a porous trail. A hydrodynamic approach makes it evident that the active particle generates a long-range density wake which breaks fore-aft symmetry, consistent with the simulations. Accounting for the back-reaction of the compressible medium leads to (i) dynamical jamming of the active particle, and (ii) a dynamical non-reciprocal attraction between two active particles moving along the same direction, with the trailing particle catching up with the leading one in finite time. We emphasize that these nonreciprocal effects appear only when the active particles are moving and so manifest in the vicinity of the jamming-unjamming transition.
在稠密的可压缩粘弹性流体中的活性布朗粒子稀悬浮液，构成了研究动态相变过程中非互易性出现的自然环境。在这些密度下，活性粒子的输运受到被动介质的强烈影响，并表现出作为活性和介质密度函数的动态堵塞转变。在此过程中，可压缩介质被积极搅动——对于低活性，活性粒子会自我困在其自身形成的腔中，而对于高活性，活性粒子会穿过介质，要么伴随着移动的各向异性尾流，要么留下多孔轨迹。一种流体动力学方法表明，活性粒子会产生一个破坏前后对称性的长程密度尾流，这与模拟结果一致。考虑可压缩介质的反作用会导致：（i）活性粒子的动态堵塞，以及（ii）沿相同方向移动的两个活性粒子之间的动态非互易吸引，尾随粒子会在有限时间内追上领先粒子。我们强调，这些非互易效应仅在活性粒子移动时出现，因此在堵塞 - 解堵塞转变附近表现出来。
