发表机构
Indian Institute of Science Education and Research Mohali（印度科学教育与研究学院穆哈里分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究在含两种化学物质的活性流体中发现了极端事件，其出现与佩克莱数及非线性增长项相关，并可通过降阶模型复现，对主动输运生物现象有潜在意义。
AI 中文摘要
我们观察到在一种活性流体中出现了极端事件，该流体包含两种不同的化学物质，它们调节活性应力。其中一种物质扩散缓慢，另一种扩散迅速，快速扩散物质的增长通过非线性逻辑斯蒂项进行建模。我们通过时间序列、分岔图、两种物质浓度的概率分布函数、返回图以及事件间间隔分布的分析，证明了在孤子状合并-涌现动力学和时空混沌的机制中，浓度的时间演化以及系统的空间分布上均存在极端事件。有趣的是，我们还发现在孤子状机制中，慢速化学物质存在明显的极端事件和超极端事件的聚集现象。我们进一步系统地探索了极端事件发生对佩克莱数和非线性增长项强度的依赖性，发现极端事件的概率在超过临界佩克莱数后增加，而增加非线性则会抑制极端事件。最后，为了获得更深入的见解，我们研究了一个修正的模态截断降阶模型，该模型由模拟该活性流体系统的耦合微分方程组成。我们发现该降阶模型也表现出极端事件，其出现与吸引子尺寸因吸引子危机而突然扩大相关。这些结果表明活性流体系统中存在极端事件，并且对主动输运起重要作用的生物现象具有潜在的相关性。
英文摘要
We observe the emergence of extreme events in an active fluid involving two distinct chemical species that regulate active stress. One species is slow diffusing and the other is fast diffusing, and the growth of the fast-diffusing species is modelled using a nonlinear logistic term. We demonstrate the presence of extreme events in the temporal evolution of the concentrations, as well as in the spatial profile of the system,in regimes of merging-emerging soliton-like dynamics and spatio-temporal chaos, through analysis of the time-series, bifurcation diagrams, probability distribution functions of the concentration of the two species, return maps and distributions of inter-event intervals. Interestingly, we also find evidence of pronounced bunching of extreme events and super-extreme events in the slow chemical species in the soliton-like regime. We go on to systematically explore the dependence of the extreme event occurrences on the Péclet number and the strength of the nonlinear growth term, and find that the probability of extreme events increases after a critical Péclet number, while increasing the nonlinearity suppresses extreme events. Lastly, in order to gain further insight, we investigate a modified mode-truncated reduced order model comprising of coupled differential equations mimicking this active fluid system. We find that this reduced order model also exhibits extreme events whose emergence is correlated with a sudden expansion in attractor size due to a crisis arising from attractor collision.So these results demonstrate the existence of extreme events in an active fluid system, and are of potential relevance to biological phenomena where active transport plays an important role.
