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.

Workshop on “Beyond mean field theory”

About 100 physicists from all over the world got together in Rome at the start of the 2018 to discuss recent advances to go beyond mean-field theory in statistical physics and statistical field theory. Researchers from different horizons — studying glasses, disordered systems, many-body localization, conformal field theory and others — looked for synergies at the rapidly evolving interfaces between these subfields. The event was funded by the Simons Collaboration on “Cracking the glass problem” but also featured a session on conformal bootstrap, which is the subject of another Simons Collaboration. The gathering was also the occasion to honor the life and the memory of Cyrano De Dominicis, who made key contributions to these different topics during his long and illustrious career.

The slides will be made available on the workshop home page:


Workshop: Yielding of amorphous solids

A workshop on the recent advances of the yielding transition in amorphous solids took place in Paris on October 26-28, 2017, with the support of the Simons collaboration on Cracking the glass problem. The review talks of the six speakers spanned complementary features and pending issues of the yielding transition, studied from different theoretical perspectives. These presentations are available on the workshop website: https://sites.google.com/site/yieldingworkshop/.