Emergent Manybody Interactions Suggest Inapplicability In Practice of Hard Sphere Theory 
TYPE  Statistical & Bio Seminar 
Speaker:  Yoav G. Pollack 
Affiliation:  Weizmann Institute 
Organizer:  Yariv Kafri 
Date:  05.11.2017 
Time:  14:30  15:30 
Location:  Lidow Nathan Rosen (300) 
Abstract: 
A large effort has been devoted in the last decade to the development of an infinitedimensional meanfield theory for the jamming transition of hard spheres[1]. The lastest studies on this topic indicate that the predictions of this theory (e.g. scaling exponents) match simulation measurements in 2D/3D suprisingly well[2], seemingly suggesting that the infinitedimensional theory is relevant for realistic systems. Our current work addresses the puzzle of this lack of strong dimensional dependence usually observed in critical phenomena. We use effective interparticle forces to study the jamming transition. In thermal materials where nevertheless the mean positions are well defined on a given timescale, these effective forces are what keeps the particles ”in place”. In continuation to a recent study in which emergence of effective manybody forces was observed[3], our current work quantifies the amount of nonbinary effective interactions as a function of the closeness of jamming. We conclude that for hard spheres the effective forces are binary only at jamming, similarly to the infinitedimensional theory and propose that this explains the match of theory and measurements. Further study of the effective forces implies that the predictions of the infinitedimensional theory of hard spheres should be inapplicable to more realistic particles which are never absolutely hard[4].
