Ecole Polytechnique Federale de Lausanne
Wednesday, November 23, 2022
1:30 p.m. — Amphi Jaurès (E244)
Under cooling, a supercooled liquid undergoes a glass transition and stops flowing. Physicists do not agree on the microscopic reasons that make a glass solid. Some view this phenomenon as being collective in nature : it may be a signature of a thermodynamic phase transition, or being caused by kinetic constraints (where particles seek to solve a sort of Chinese puzzle). Others view it as simply reflecting elementary barriers for rearrangements, controlled by the elasticity of the material. Here I will focus on polydisperse numerical glasses, which are receiving a considerable attention, because they can be equilibrated as efficiently as experimental molecular liquids. I will (i) design new algorithms that can continuously speed up or slow down the normal physical dynamics, ruling out the role of a thermodynamic phase transition . (ii) Introduce a novel algorithm to systematically extract elementary rearrangements in a broad energy range. It allows to make, for the first time, a quantitative prediction on the relaxation time, assuming that relaxation is not collective in nature. The comparison with observation is excellent . (iii) I will explain why, in such a scenario, dynamical correlations emerge even if they have little effects on the dynamics . (iv) I will discuss the nature of elementary rearrangements under cooling, and how these aspects relate to mean field description of glasses.
 ongoing work with Cristina Gavazzoni and Carolina Brito
 ongoing work with Wencheng Ji and Massimo Pica Ciamarra
 ongoing work with Giulio Biroli, Misaki Ozawa, Marko Popovic and Ali Tahaei
 joint work with Wencheng Ji, Tom WJ de Geus and Elisabeth Agoritsas