arXiv 1607.044782016-07cond-mat.softcond-mat.stat-mechphysics.bio-ph

自推进粒子的活性稠密体系的粘度和有效温度

Viscosity and effective temperature of an active dense system of self-propelled particles

Saroj Kumar Nandi

备注：: Total 7 pages

摘要：

我们得到一个非平衡理论的一个简单的模型的一般类的活跃的致密系统组成的自推进粒子的自推进力，$f_0$，和持久时间，$τ_p$，他们的运动。我们考虑两种模型的活动，并发现系统的特点是不断变化的有效温度$T_{eff}(τ)$，通过广义波动耗散定理定义。$T_{eff}(τ)$在很短时间内等于平衡温度$τ$，在很长时间内饱和到$T_{eff}=T_{eff}(τ\to\infty)$; $T_{eff}(τ)$达到长时间极限时的过渡时间$t_{trans}$取决于$τ_p$单独和两种模型的$t_{trans}\sim τ_p^{0.85}$。$f_0$随着活性的增加而降低粘度，另一方面，$τ_p$可以根据如何包括活性的细节来增加或降低粘度。然而，作为$T_{eff}$的函数，对于不同的活性模型和$η\sim (T_{eff}-T)^{-γ}$与$γ=1.74$，粘度显示出相同的行为。我们的理论与实验数据相比，给出了合理的协议，并与不同系统的几个实验是一致的。

英文摘要：

We obtain a nonequilibrium theory for a simple model of a generic class of active dense systems consisting of self-propelled particles with a self-propulsion force, $f_0$, and persistence time, $τ_p$, of their motion. We consider two models of activity and find the system is characterized by an evolving effective temperature $T_{eff}(τ)$, defined through a generalized fluctuation-dissipation theorem. $T_{eff}(τ)$ is equal to the equilibrium temperature at very short time $τ$ and saturates to $T_{eff}=T_{eff}(τ\to\infty)$ at long times; The transition time $t_{trans}$ when $T_{eff}(τ)$ goes to the long-time limit depends on $τ_p$ alone and $t_{trans}\sim τ_p^{0.85}$ for both models. $f_0$ reduces the viscosity with increasing activity, $τ_p$ on the other hand, may increase or decrease viscosity depending on the details of how the activity is included. However, as a function of $T_{eff}$, viscosity shows the same behavior for different models of activity and $η\sim (T_{eff}-T)^{-γ}$ with $γ=1.74$. Our theory gives reasonable agreement when compared with experimental data and is consistent with several experiments on diverse systems.

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