Thermodynamics of Microscopic Systems far from Equilibrium

我的博士学位将包括一些以研究微观远离平衡系统为主题的项目。正如EPSRC的物理科学战略中强调的那样，近几十年来，人们对新兴现象和非平衡热力学的物理学的兴趣急剧增长。虽然我们对大型复杂系统的理解已经取得了很大的进步，但关于潜在的微观物理的某些基本问题仍然没有得到回答。我研究的一个目标是更好地理解描述系统的详细程度和该系统的热力学性质之间的关系。当某些非平衡系统的部分演化被隐藏时，它们就会显得“类似于平衡”。这既是一个实际问题，也是一个理论问题；观察者很少能接触到实验系统的每一个微观细节。在我的研究中，我试图量化一个简单系统在完全知识和部分知识条件下的熵产生率，这是一种距离均衡的距离的度量。虽然以前的研究试图对这些部分隐藏的系统中的熵产生施加一般界限，但我们采用了微扰方法来更精确地量化熵产生速率。希望这项工作对寻求量化细胞、细菌和其他形式生命的能量学的实验科学家具有实际意义。与此同时，我对从游泳微生物中提取有用能量感兴趣。近年来，建造一台由微生物提供动力的“主动发动机”的前景引起了人们的兴趣。我和帝国理工学院的合作者在理论上限定了从单个随机自推进电池中可以提取的最大功量，在现实的约束下，它的自推进能力不能直接测量。这项工作的潜在影响是显而易见的；人们希望主动发动机能够提供一种灵活的、无休止的可持续能源。他们甚至被建议作为航天器和卫星的一种可能的动力源。这项工作与EPSRC的战略主题密切相关，即“浮现和物理远离平衡”。我研究的是微观的、远离平衡的物理系统，这些系统构成了在研究活性物质时出现的新现象的基石，例如聚集和运动诱导的相分离。通过这种自下而上的方法，我希望为我们对现实的非平衡系统建模的理解和能力做出贡献。

My PhD will consist of a number of projects themed around the study of microscopic far-from-equilibrium systems. As highlighted in the EPSRC's physical sciences strategy, interest in the physics of emergent phenomena and non-equilibrium thermodynamics has grown dramatically in recent decades. Whilst great advances have been made in our understanding of large, complex systems, certain fundamental questions about the underlying microscopic physics remain unanswered. One objective of my research is to better understand the relationship between the level of detail at which a system is described and the thermodynamic properties of that system. Certain non-equilibrium systems appear "equilibrium-like" when parts of their evolution are hidden. This is a practical as well as a theoretical concern; observers rarely have access to every microscopic detail of experimental systems. In my research I seek to quantify the entropy production rate, a measure of distance from equilibrium, of a simple system under conditions of complete and partial knowledge. Whereas previous research has sought to place general bounds on the entropy production in these partially hidden systems, we employ a perturbative approach to quantify the entropy production rate more precisely. It is hoped that this work will have be of practical importance to experimental scientists seeking to quantify the energetics of cells, bacteria and other forms of life. In parallel to this, I am interested in the extraction of useful energy from swimming microorganisms. The prospect of building an, "active engine," powered by microscopic bacteria has gathered interest in recent years. Myself and collaborators within Imperial College have placed theoretical bounds on the maximum amount of work that could hypothetically be extracted from a single stochastically self-propelling cell, under the realistic constraint that its self-propulsion cannot be directly measured. The potential impact of this work is evident; it's hoped that active engines could provide a flexible, endlessly sustainable source of energy. They have even been proposed as a possible power source for spacecraft and satellites.This work aligns closely with the EPSRC strategic theme of, "Emergence and physics far from equilibrium". I study the microscopic, far-from-equilibrium physical systems which constitute the building blocks of the emergent phenomena which arise in the study of active matter, such as flocking and motility-induced phase separation. Through this bottom-up approach, I hope to offer a contribution to our understanding and ability to model realistic non-equilibrium systems.