Shearing Rheology and Glassy Behavior in Athermal and Thermalized Models of Granular Materials, Simple Liquids, and Amorphous Solids

该奖项支持理论研究和教育的平衡和驱动非平衡临界现象的性质在颗粒材料，玻璃状形成简单的液体，以及相关的软物质系统，如泡沫，乳液和胶体。通过广泛的数值模拟，PI将研究干扰相图的新区域，这些区域表征了从流动的类液体状态到刚性但结构无序状态转变的各种物理系统。研究将集中在以下方面：(i) PI将研究非热非晶固体在干扰下的流变学，表征接近屈服应力时的单一行为，并探索其与动态非均质性的关系。PI将研究热玻璃化行为与非热干扰转变之间的关系。低温和低剪切应变速率下的剪切驱动稳态将被用作证明是否存在真正的奇异热玻璃化转变的新探针。（iii） PI将探讨不同动力学对感兴趣的关键行为的影响，特别是粘性耗散的平均场和非平均场模型之间的差异，以及从惯性到过阻尼动力学的交叉。（iv） PI将研究摩擦力对剪切驱动的非热干扰的影响。在模拟中探索新型剪切卡塞状态的实验观察。PI将检查不同的摩擦模型，滑动接触与几何凹凸对模拟现象的影响。这些研究还将讨论平衡统计力学的概念和方法对基本非平衡系统和驱动稳态的适用性。本科生将参与研究，获得对现代数值模拟科学研究和方法的经验、技能和见解。罗切斯特大学有几个现场REU项目，极大地帮助吸引高质量的本科生参加暑期研究项目。他们中的许多人在接下来的一年里继续进行高级项目或论文。该项目涉及与瑞典Ume - a大学以及杜克大学、耶鲁大学和罗切斯特大学的其他研究小组的国际合作。这些互动将为学生提供直接面对理论与实验的机会，使用最先进的高性能计算平台。该奖项支持颗粒状和玻璃状材料的理论研究和教育，重点研究颗粒状材料、泡沫、胶体、乳剂和冷却成玻璃状的液体从流动的液体状态到具有无定形结构的刚性状态的明显转变的性质。对颗粒状和玻璃状材料的理解不仅具有内在的科学兴趣，而且对各种工业过程都很重要，从药品加工到种子和谷物的运输，再到材料制造。这项研究将有助于建立颗粒状和玻璃状材料的知识库，并可能导致现代工业和技术许多重要领域效率的进步和提高。通过广泛的数值模拟，PI将探索干扰相图的未知区域，该相图描绘了材料从流动的类液体状态转变为刚性但结构无序状态的条件。干扰跃迁发生在远离稳定平衡状态的地方。在非平衡统计力学理论尚未得到很好发展的情况下，研究平衡统计力学的概念和方法在非平衡系统和驱动稳态领域的应用或适应程度是一个重要的研究方向。PI将为这一努力作出贡献。PI将探索干扰转变和冷却液体变成玻璃的转变之间的关系。由于颗粒系统中的能量尺度通常比温度高，因此温度通常不会在干扰转变中起作用。PI将使用一种新颖的策略和创新的技术来研究足够高温度下的干扰转变的性质，并将温度下的干扰转变与玻璃化转变的特征进行比较。颗粒系统的研究往往忽略颗粒之间的摩擦，但仍然能够观察到干扰转变。PI计划研究发生在真实颗粒材料中的摩擦力对干扰的影响。PI将通过模拟研究不同的模型，以阐明在剪切应变的应用下发生的新型堵塞状态的实验观察。本科生将参与研究，获得对现代数值模拟科学研究和方法的经验、技能和见解。罗切斯特大学有几个现场REU项目，极大地帮助吸引高质量的本科生参加暑期研究项目。他们中的许多人在接下来的一年里继续进行高级项目或论文。该项目涉及与瑞典Ume - a大学以及杜克大学、耶鲁大学和罗切斯特大学的其他研究小组的国际合作。这些互动将为学生提供直接面对理论与实验的机会，使用最先进的高性能计算平台。

TECHNICAL SUMMARYThis award supports theoretical research and education on the nature of equilibrium and driven nonequilibrium critical phenomena in granular materials, glassy forming simple liquids, and related soft matter systems such as foams, emulsions and colloids. Using extensive numerical simulations, the PI will investigate new regions of the jamming phase diagram that characterize a diverse array of physical systems that undergo transitions from flowing liquid-like states to rigid but structurally disordered states. The research will focus on the following activities: (i) The PI will study the rheology of athermal amorphous solids above jamming, characterizing the singular behavior as one approaches the yield stress, and exploring the relation to dynamic heterogeneity. (ii) The PI will investigate the relationship between thermal glassy behavior and the athermal jamming transition. Shear driven steady states at low temperature and low shear strain rate will be used as a new probe to demonstrate whether a true singular thermal glass transition exists. (iii) The PI will explore the effect of different dynamics on the critical behaviors of interest, in particular the difference between mean-field and non-mean-field models of viscous dissipation, and the crossover from inertial to overdamped dynamics. (iv) The PI will study the effect of frictional forces on shear driven athermal jamming. The experimental observation of novel shear jammed states will be explored in simulations. The PI will examine the effect differing models for friction, sliding contacts as opposed to geometric asperities, have on simulation phenomena. These investigations will also address the applicability of concepts and methods from equilibrium statistical mechanics to fundamentally nonequilibrium systems and driven steady states.Undergraduate students will participate in the research, gaining experience, skill, and insight into modern scientific research and methods of numerical simulation. The University of Rochester has several site REU programs that greatly assist in attracting high quality undergraduate students to work on summer research projects. Many of these continue with senior projects or theses during the following year. This project involves international collaboration with Ume¢ªa University in Sweden, as well as other research groups at Duke, Yale, and Rochester. These interactions will provide students with the opportunity to directly confront theory with experiment, to use state of the art high performance computing platforms.NON-TECHNICAL SUMMARYThis award supports theoretical research and education on granular and glassy materials with an emphasis to investigate the nature of the apparent transitions from a flowing liquid-like state to a rigid state with an amorphous structure that occur in granular materials, foams, colloids, emulsions, and liquids cooled to become a glass. The understanding of granular and glassy materials is not only of intrinsic scientific interest, but is important for a wide variety of industrial processes, from the processing of pharmaceuticals, to transportation of seeds and grains, to materials fabrication. This research will contribute to the knowledge base on granular and glassy materials and may lead to advances and improvements in efficiency in many important areas of modern industry and technology. Using extensive numerical simulations, the PI will explore uncharted regions of the jamming phase diagram, a diagram that charts the conditions under which materials undergo transitions from flowing liquid-like states to rigid but structurally disordered states. The jamming transition occurs far from the steady state of equilibrium. While the theory of nonequilibrium statistical mechanics is not well developed, an important research direction is to investigate the extent to which the concepts and methods of equilibrium statistical mechanics can be applied or adapted to the realm of nonequilibrium systems and driven steady states. The PI will contribute to this effort. The PI will explore the relationship between the jamming transition and the transition where a cooling liquid becomes a glass. Because the energy scales in granular systems are usually very high compared to the temperature, temperature does not normally play a role in the jamming transition. The PI will use a novel strategy and innovative techniques to study the nature of the jamming transition at sufficiently high temperatures and compare the signatures of the jamming transition at temperature to the glass transition. Studies of granular systems often neglect friction between particles, but nonetheless are able to observe the jamming transition. The PI plans to study the effect of frictional forces that occur in real granular materials on jamming. The PI will investigate different models through simulation to illuminate experimental observations of novel jammed states that occur under the application of shear strain. Undergraduate students will participate in the research, gaining experience, skill, and insight into modern scientific research and methods of numerical simulation. The University of Rochester has several site REU programs that greatly assist in attracting high quality undergraduate students to work on summer research projects. Many of these continue with senior projects or theses during the following year. This project involves international collaboration with Ume¢ªa University in Sweden, as well as other research groups at Duke, Yale, and Rochester. These interactions will provide students with the opportunity to directly confront theory with experiment, to use state of the art high performance computing platforms.