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# Applied Mathematics Colloquium – Silke Henkes, School of Mathematics, University of Bristol

## November 6, 2020 @ 9:15 am - 10:30 am

Date: Friday, November 6th, 2020

Time: **9:15 am**

Title and abstract:

Rigidity percolation and frictional jamming

In jamming of frictional granular particles, rigidity emerges over a range of mean contact numbers and densities, unlike in frictionless jamming where Maxwell constraint counting determines the isostatic point. I will introduce the (3,3) frictional pebble game and frictional rigidity percolation for frictional jamming. For simulated and experimental packings, we find a second-order rigidity transition where rigid and floppy regions coexist. The experimental location of the rigidity transition is at z=2.4, well below the mean field isostatic bound of z=3.

Stress data are consistent with a picture where a load-bearing rigid backbone emerges with rising contact number, with the floppy regions corresponding to ‘rattlers’. We pair these results with a thorough study of frictional rigidity percolation on a lattice model. It shows that it is part of a separate universality class to central force rigidity percolation, with a new mechanism of propagating spanning rigid clusters through rigid hinges.