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.