邀请人：厚美瑛 研究员（mayhou@iphy.ac.cn）

报告摘要：
Granular matter, such as soils, powders, and grains, is ubiquitous in natural and industrial contexts. Being inherently athermal and dissipative, it cannot be understood as ordinary state of matter (Newtonian fluid or elastic solid) and display rich anomalies under different external drivings (vibration, shearing, and etc). Thriving studies on granular matter since the 1990s have driven major advances in soft matter or complex fluid communities, though largely phenomenological. Particularly, growing evidences have indicated a deeper theoretical connection between granular matter with glassy materials. Based on my recent work, I will elaborate this point mainly from three aspects. (1) The existence of mechanically stable granular packings depends on external driving. From systematical experiments, I will show that the internal variable of these various disordered packings, namely effective temperature, is simply determined by the driving intensity. This reflects how an out-of-equilibrium statistical mechanics framework functions in granular matter. (2) From another cyclic shearing experiment, I will discuss the anomalous relaxation process of granular matter, in sharp contrast with standard amorphous materials, that no elastic regime can be identified. I will explain how particle roughness alters the relaxation pathway by comparing two granular systems. (3) Closely related to (2), I will numerically establish the state diagram of granular compaction process as functions of cyclic shearing amplitude and friction. By highlighting the interplay between mechanical stability and intrinsic aging, this will demonstrate how a frictional granular system deviates from other amorphous solids, which is typically described by frictionless soft spheres. To conclude, integrating granular matter with glassy/soft-matter systems advances a unified understanding of complex materials.   

[1] Yuan, Y., Xing, Y., Zheng, J., Li, Z., Yuan, H., Zhang, S., ... & Wang, Y. (2021). Experimental test of the Edwards volume ensemble for tapped granular packings. Physical Review Letters, 127(1), 018002.    
[2] Xing, Y., Yuan, Y., Yuan, H., Zhang, S., Zeng, Z., Zheng, X., ... & Wang, Y. (2024). Origin of the critical state in sheared granular materials. Nature Physics, 20(4), 646-652.
[3] Yuan, Y., Zeng, Z., Xing, Y., Yuan, H., Zhang, S., Kob, W., & Wang, Y. (2024). From creep to flow: Granular materials under cyclic shear. Nature Communications, 15(1), 3866.
[4] Yuan, Y., Kob, W., & Tanaka, H. (2025). Friction-controlled reentrant aging and fluidization in granular materials. arXiv preprint arXiv:2510.15360.

报告人简介：
袁野，于2015年和2020年在北京大学工学院力学与工程科学系获得工程力学学士和博士学位（导师：李水乡）。2020年博士毕业后加入上海交通大学物理与天文学院王宇杰课题组，开展博士后研究工作。2023年加入东京大学Hajime Tanaka课题组，继续开展博士后研究工作至今。从事颗粒物质、软凝聚态物理等方向的研究，主要关注颗粒物质、玻璃（非晶）态物质等系统的物理和力学性质。关于颗粒物质无序堆积、非平衡态液固转变（例如阻塞转变、玻璃化转变）、颗粒物质的统计物理与流变学等课题，结合数值模拟和实验测量手段开展工作。迄今已发表学术论文20篇，其中以第一作者身份在PNAS (in press)、PRL、Nature Communications等期刊发表多项成果。