Scalar φ4 field theory for active-particle phase separation
Scalar φ4 field theory for active-particle phase separation
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DOI：
10.1038/ncomms5351
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发表时间：
2013-11
影响因子：
16.6
通讯作者：
R. Wittkowski;A. Tiribocchi;Joakim Stenhammar;R. Allen;D. Marenduzzo;M. Cates
中科院分区：
文献类型：
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作者：
R. Wittkowski;A. Tiribocchi;Joakim Stenhammar;R. Allen;D. Marenduzzo;M. Cates
最近的理论预测了定向无序的活性粒子之间的相分离，这些粒子的推进速度随着密度的下降足够快。这一过程的粗粒度模型显示，均匀状态下时间反转对称性(详细平衡)可以恢复，但被梯度项破坏；因此，详细平衡破坏与界面现象强烈耦合。为了探索这种耦合所产生的微妙的类属物理，我们在这里介绍“主动模型B”。这是一个标量φ4场论(或相场模型)，它通过一个前导阶方向梯度项最大限度地破坏了详细平衡。我们发现，这一附加项对粗化动力学的影响不大，但通过在平坦界面上产生(热力学)压力的跃升，改变了静态相图。这两个结果都令人惊讶，因为界面现象总是强烈地与粗化动力学有关，但在详细平衡系统中，与相平衡无关。
Recent theories predict phase separation among orientationally disordered active particles whose propulsion speed decreases rapidly enough with density. Coarse-grained models of this process show time-reversal symmetry (detailed balance) to be restored for uniform states, but broken by gradient terms; hence, detailed-balance violation is strongly coupled to interfacial phenomena. To explore the subtle generic physics resulting from such coupling, we here introduce ‘Active Model B’. This is a scalarφ4field theory (or phase-field model) that minimally violates detailed balance via a leading-order square-gradient term. We find that this additional term has modest effects on coarsening dynamics, but alters the static phase diagram by creating a jump in (thermodynamic) pressure across flat interfaces. Both results are surprising, since interfacial phenomena are always strongly implicated in coarsening dynamics but are, in detailed-balance systems, irrelevant for phase equilibria.