Dynamics in dense mixtures: Kinetics versus thermodynamics in non-equilibrium fluctuations, phase separation and structure formation

非平衡弛豫是实验物理和理论物理中的一个重要现象。对于稠密的多组分混合物尤其如此，它们在自然界中普遍存在--在生物流体中--如细胞质--以及软物质中--例如在胶体悬浮液中。由于分馏，这种混合物已经处于平衡状态，表现出复杂的相行为，不同类型的颗粒在相之间的分配不均匀。非平衡过程，如淬火后的相分离，继承了所有这些热力学复杂性，但包含了作为另一个重要组成部分的动力学效应。这些动力学效应由连续介质方法中的迁移率描述，在稠密系统中具有重要的结构，因为不同粒子物种在相反方向上的运动可能比集体粒子运动慢得多或快得多。这可能会导致相分离中出现多个时间尺度和长寿命的非平衡结构等新现象，这些现象才刚刚开始被探索。本项目将从理论上研究稠密混合物的动力学，以解决这一领域的许多开放挑战。它的主要新奇之处在于将胶体和生物混合物的极限情况与它们相当不同的热力学联系在一起，并研究了在稠密、缓慢的混合物中可能发生的非平凡动力学。通过这种方式，该项目旨在通过解决一些关键的悬而未决的问题，实现我们对稠密混合物物理学的理解的一步改变，同时开发新的方法，例如系统地推导迁移率，这将为未来的广泛工作开辟道路。这项雄心勃勃的研究计划需要并明确旨在利用两个私人投资机构为项目带来的独特专业知识组合。其中包括用于非平衡液体的粗粒化技术和连续体法(M.Krüger)，以及用于大混合物中相分离的投影法(P.Sollich)。

Non-equilibrium relaxation is an important phenomenon of fundamental interest in experimental and theoretical physics. This is especially so for dense multi-component mixtures, which are ubiquitous in nature -- in biological fluids such as the cytoplasm -- as well as in soft matter -- for example in colloidal suspensions. Already at equilibrium such mixtures exhibit complex phase behaviour due to fractionation, where particles of different type partition themselves unevenly between phases. Non-equilibrium processes such as phase separation after a quench inherit all of this thermodynamic complexity but contain kinetic effects as a further important ingredient. These kinetic effects, which are described by mobilities in continuum approaches, carry significant structure in dense systems because e.g. movement of different particle species in opposite directions can be much slower or faster than collective particle motion. This can lead to novel phenomena like the emergence of multiple timescales and long-lived non-equilibrium structures in phase separation, which have only begun to be explored.This project will study the dynamics of dense mixtures theoretically to address the many open challenges in this area. Its main novelty lies in connecting the limiting cases of colloidal and biological mixtures with their rather different thermodynamics, and in studying the non-trivial kinetics that can occur in dense, slow mixtures. In this way the project aims to achieve a step change in our understanding of the physics of dense mixtures, by tackling a number of key open questions, while at the same time developing new methodologies for e.g. the systematic derivations of mobilities that will open the way for a broad range of future work. The ambitious research plan requires, and is designed explicitly to exploit, the unique combination of expertise that the two PIs bring to the project. These include coarse-graining techniques and continuum approaches for non-equilibrium liquids (M. Krüger) and projection methods for phase separation in large mixtures (P. Sollich).