论文标题

非均值Vicsek型集体行为模型

Non-mean-field Vicsek-type models for collective behaviour

论文作者

Buttà, P., Goddard, B., Hodgson, T. M., Ottobre, M., Painter, K. J.

论文摘要

我们考虑在非均值场状态下与Vicsek类型相互作用及其宏观PDE极限进行相互作用。也就是说,我们考虑系统中的每个粒子/试剂仅与系统中粒子的规定子集相互作用(例如,在一定距离内的粒子)。在这个非均值场式中,可以通过系统中的代理总数(\ textIt {global缩放})或与粒子有效相互作用(\ textIt {local scaleing})的代理数量(\ textIt {global缩放})之间的影响(\ textIt {global caliging})之间的影响归一化。我们在许多方面比较了全球缩放和局部缩放系统的行为,考虑到每个缩放PDE和相应的粒子模型。特别是,我们观察到,在某些参数方案中,本地和全球尺度的粒子系统都表现出模式形成(即形成类似波浪的溶液的形成),并且通常显示出相似的动力学。相应的PDE模型并非如此。确实,尽管这两个PDE模型都具有多个固定状态,但对于全球缩放的PDE,这种(空间均匀)平衡对于某些参数制度是不稳定的,而不稳定性会导致行驶波解决方案,而它们始终稳定在本地规模的范围内,从未产生行进波。该观察结果基于对模型的仔细数值研究,并得到进一步分析的支持。

We consider interacting particle dynamics with Vicsek type interactions, and their macroscopic PDE limit, in the non-mean-field regime; that is, we consider the case in which each particle/agent in the system interacts only with a prescribed subset of the particles in the system (for example, those within a certain distance). In this non-mean-field regime the influence between agents (i.e. the interaction term) can be normalised either by the total number of agents in the system (\textit{global scaling}) or by the number of agents with which the particle is effectively interacting (\textit{local scaling}). We compare the behaviour of the globally scaled and the locally scaled systems in many respects, considering for each scaling both the PDE and the corresponding particle model. In particular we observe that both the locally and globally scaled particle system exhibit pattern formation (i.e. formation of travelling-wave-like solutions) within certain parameter regimes, and generally display similar dynamics. The same is not true of the corresponding PDE models. Indeed, while both PDE models have multiple stationary states, for the globally scaled PDE such (space-homogeneous) equilibria are unstable for certain parameter regimes, with the instability leading to travelling wave solutions, while they are always stable for the locally scaled one, which never produces travelling waves. This observation is based on a careful numerical study of the model, supported by further analysis.

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