Boundary information inflow enhances correlation in flocking.
Boundary information inflow enhances correlation in flocking.
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边界信息流入增强了聚集的相关性。
DOI：
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发表时间：
2012
影响因子：
8.6
通讯作者：
F. Ginelli
中科院分区：
文献类型：
--
作者：
A. Cavagna;I. Giardina;F. Ginelli
动物集体行为最显著的特征是高度有序结构的出现。远距离空间相关性的存在，虽然肉眼看不太明显，但也许是自我组织的一个更深刻的标志。三维椋鸟群的实验数据表明，速度相关函数C（r）~1/r（γ）的衰减指数非常小，γ<<1。这一结果既不能用平衡场论来解释，也不能用非平衡理论和主动系统的模拟来解释。在这里，通过数值模拟和理论计算，我们表明，一个动态场施加到一组海森堡自旋的边界上的三维晶格产生一个消失的指数γ，在八哥群。动力场的作用是产生从边界到体块的信息流入，触发长程自旋波模式，从而产生有害的长程相关。这种现象的生物学起源可以是外源性的--环境扰动产生的信息从群体的边界传递到群体的主体--也可以是内源性的--群体使自己保持在一个恒定的动态激发状态，这有利于相关性和集体反应。
The most conspicuous trait of collective animal behavior is the emergence of highly ordered structures. Less obvious to the eye, but perhaps more profound a signature of self-organization, is the presence of long-range spatial correlations. Experimental data on starling flocks in 3D show that the exponent ruling the decay of the velocity correlation function, C(r)~1/r(γ), is extremely small, γ<<1. This result can neither be explained by equilibrium field theory nor by off-equilibrium theories and simulations of active systems. Here, by means of numerical simulations and theoretical calculations, we show that a dynamical field applied to the boundary of a set of Heisenberg spins on a 3D lattice gives rise to a vanishing exponent γ, as in starling flocks. The effect of the dynamical field is to create an information inflow from border to bulk that triggers long-range spin-wave modes, thus giving rise to an anomalously long-ranged correlation. The biological origin of this phenomenon can be either exogenous-information produced by environmental perturbations is transferred from boundary to bulk of the flock-or endogenous-the flock keeps itself in a constant state of dynamical excitation that is beneficial to correlation and collective response.