In a system of colloidal inclusions suspended in an equilibrium bath of smaller particles, the particulate bath engenders effective, short-ranged, primarily attractive interactions between the inclusions, known as depletion interactions, that originate from the steric depletion of bath particles from the immediate vicinity of the inclusions. In a bath of active (self-propelled) particles, the nature of such bath-mediated interactions can qualitatively change from attraction to repulsion, and they become stronger in magnitude and range of action as compared with typical equilibrium depletion interactions, especially as the bath activity (particle self-propulsion) is increased. We study effective interactions mediated by a bath of active Brownian particles between two fixed, impenetrable, and disk-shaped inclusions in a planar (channel) confinement in two dimensions. Confinement is found to strongly influence the effective interaction between the inclusions, specifically by producing alternating interaction profiles with possible attractive and repulsive regions in sufficiently narrow channels. We study the dependence of the ensuing interactions on different system parameters and the orientational (parallel versus perpendicular) configuration of the inclusion pair relative to the channel walls. The confinement effects are largely regulated by the layering of active particles next to the surface boundaries, both of the inclusions and the channel walls that counteract one another in accumulating the active particles in their own proximities. In narrow channels, the combined effects due to the channel walls and the inclusions lead to peculiar structuring of active particles (reminiscent of wavelike interference patterns) within the channel.

中文翻译：

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约束流体在活性流体中夹杂物之间的交替相互作用

在悬浮于较小颗粒的平衡浴中的胶体夹杂物系统中，颗粒浴在夹杂物之间产生有效的，短程的，主要是有吸引力的相互作用，称为耗尽相互作用，这是由于浴颗粒从紧邻区域的空间耗尽而引起的。内含物。在活性（自推进式）颗粒浴中，这种浴介导的相互作用的性质可以从吸引到排斥发生质变，并且与典型的平衡耗竭相互作用相比，它们的作用强度和作用范围变得更强，尤其是在浴中活动（粒子自推进）增加。我们研究了在两个固定的，不可穿透的，以及平面（通道）约束中的二维盘状夹杂物。发现限制作用强烈影响夹杂物之间的有效相互作用，特别是通过在足够狭窄的通道中产生可能具有吸引力和排斥性区域的交替相互作用曲线。我们研究了随之而来的相互作用对不同系统参数的依赖性以及夹杂物对相对于通道壁的定向（平行与垂直）构型。限制作用在很大程度上由邻近表面边界的活性颗粒的分层来调节，内含物和通道壁在它们各自附近累积活性颗粒时相互抵消。在狭窄的渠道中