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首页> 外文期刊>new journal of physics >Time-reversal symmetry violations and entropy production in field theories of polar active matter
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Time-reversal symmetry violations and entropy production in field theories of polar active matter

机译：极地活性物质场论中的时间反转对称性违反和熵产生

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We investigate the steady-state entropy production rate (EPR) in the hydrodynamic Vicsek model (HVM) and diffusive flocking model (DFM). Both models display a transition from an isotropic gas to a polar liquid (flocking) phase, in addition to travelling polar clusters and microphase-separation in the miscibility gap. The phase diagram of the DFM, which may be considered an extension of the HVM, contains additional structure at low densities where we find a novel crystal phase in which a stationary hexagonal lattice of high-density ridges surround low density valleys. From an assessment of the scaling of the EPR at low noise, we uncover that the dynamics in this limit may be organised into three main classes based on the dominant contribution. Truly nonequilibrium dynamics is characterised by a divergent EPR in this limit, and sustains global time-reversal symmetry (TRS) violating currents at zero noise. On the other hand, marginally nonequilibrium and effectively equilibrium dynamics have a finite EPR in this limit, and TRS is broken only at the level of fluctuations. For the latter of these two cases, detailed balance is restored in the small noise limit and we recover effective Boltzmann statistics to lowest nontrivial order. We further demonstrate that the scaling of the EPR may change depending on the dynamical variables that are tracked when it is computed, and the protocol chosen for time-reversal. Results acquired from numerical simulations of the dynamics confirm both the asymptotic scaling relations we derive and our quantitative predictions.
机译：我们研究了流体动力学Vicsek模型（HVM）和扩散植绒模型（DFM）中的稳态熵产生率（EPR）。两种模型都显示了从各向同性气体到极性液相（植绒）相的转变，此外还有行进的极性团簇和混溶间隙中的微相分离。DFM的相图可以被认为是HVM的延伸，它包含低密度下的附加结构，我们发现了一种新的晶相，其中高密度脊的静止六边形晶格围绕着低密度山谷。通过对低噪声下EPR缩放的评估，我们发现该限值的动态可以根据主要贡献分为三个主要类别。真正的非平衡动力学的特征是在此限值内具有发散的 EPR，并在零噪声下维持违反电流的全局时间反转对称性 （TRS）。另一方面，边际非平衡动力学和有效平衡动力学在此极限内具有有限的 EPR，并且 TRS 仅在波动水平上被打破。对于这两种情况中的后一种情况，在小噪声限值中恢复了详细平衡，并将有效的玻尔兹曼统计恢复到最低非平凡阶。我们进一步证明，EPR的缩放可能会根据计算时跟踪的动态变量以及为时间反转选择的协议而改变。从动力学的数值模拟中获得的结果证实了我们推导的渐近标度关系和定量预测。

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