Beg Rohu Summer School 2019

The Beg Rohu Summer School 2019 edition on “Glasses, Jamming, and Slow Dynamics” featured lectures by collaboration members Ludovic Berthier, Andrea Liu, Gilles Tarjus and Francesco Zamponi. All the lectures have been video recorded and are available on this YouTube playlist

A stability-reversibility map for glasses

Amorphous solids have complex responses to deformations, with substantial consequences in material design and applications. In this respect, two intertwined aspects are important: stability and reversibility. It is crucial to understand, on the one hand, how a glass may become unstable due to increased plasticity under shear deformations, and, on the other hand, to what extent the response is reversible, meaning how much a system is able to recover the original configuration once the perturbation is released. In an article appeared on Science Advances (http://advances.sciencemag.org/content/4/12/eaat6387 ), Yuliang Jin, Pierfrancesco Urbani, Francesco Zamponi, and Hajime Yoshino focused on assemblies of hard spheres as the simplest model of a colloidal glasses and granular matter. They exhaustively mapped out the stability and reversibility of the glass under volume and shear strains using extensive numerical simulations. Their study provides a unified framework for understanding elasticity, plasticity, yielding, and jamming in amorphous solids.

See here [link: https://phys.org/news/2018-12-amorphous-solids-elastic-plastic.html]
and here [link: https://phys.org/news/2018-12-adventures-phase-space-plastic-elastic.html]
for more details.

A new universality class for jamming of nonspherical particles

The jamming transition is a key property of granular materials, including sand and dense suspensions, and it is one of the main focuses of the Simons collaboration. In the generic situation of nonspherical particles, its scaling properties are not completely understood. Previous empirical and theoretical work in ellipsoids and spherocylinders indicates that both structural and vibrational properties are fundamentally affected by shape. In a new collaborative paper appeared on PNAS ( https://doi.org/10.1073/pnas.1812457115 ), Carolina Brito, Harukuni Ikeda, Pierfrancesco Urbani, Matthieu Wyart, and Francesco Zamponi, all members of the collaboration, explain these observations. They use a combination of marginal stability arguments and the replica method to unravel a universality class for particles with internal degrees of freedom, and construct a theoretical description of its criticality.