标题： 趋同驱动的状态转变和群游鱼的双稳态 显示英文标题

标题： Confinement-driven state transition and bistability in schooling fish

摘要： 我们研究了限制密度（即单位面积可用空间中的个体数量）对极化状态到旋转状态转变的影响，使用的是在受控实验条件下的一群红鼻灯鱼（\textit{红嘴半齿脂鲤}）。我们展示了在活体动物群体中由限制密度控制的连续状态转变。在此转变过程中，鱼群表现出一种双稳态，其中极化状态和旋转状态共存，群体在两者之间随机交替。一个简单的两状态马尔可夫过程能够非常准确地描述观察到的转变。限制密度影响这种双稳态的统计特性，塑造了状态间转换时间的分布。我们的发现表明，限制在移动动物群体的状态转变中起着关键作用。更广泛地说，它们为宏观、自推进、受限代理的活性物质模型提供了实验基准。 显示英文摘要

摘要： We investigate the impact of confinement density (i.e the number of individuals in a group per unit area of available space) on transitions from polarized to milling state, using groups of rummy-nose tetra fish (\textit{Hemigrammus rhodostomus}) under controlled experimental conditions. We demonstrate a continuous state transition controlled by confinement density in a group of live animals. During this transition, the school exhibits a bistable state, wherein both polarization and milling states coexist, with the group randomly alternating between them. A simple two-state Markov process describes the observed transition remarkably well. The confinement density influences the statistics of this bistability, shaping the distribution of transition times between states. Our findings suggest that confinement plays a crucial role in state transitions for moving animal groups. More generally, they provide an experimental benchmark for active matter models of macroscopic, self-propelled, confined agents.