How do you measure the temperature of a granular packing? To start, it turns out you need to measure the forces.

Working with Karen Daniels at North Carolina State University, we investigated variables of state for a jammed granular packing by looking at the statistics of the force-networks sustained along particle contacts. A full thermodynamic theory actually needs to go further, though, as we discuss here:

E. S. Bililign, J. E. Kollmer, K. E. Daniels. Protocol-dependence and state variables in the force-moment ensemble, Physical Review Letters 122 (2019).

Wondering how this all looks in three-dimensions? With Matthias Schröter at the Institute for Multiscale Simulation and Theo 1 at FAU Erlangen, we made progress towards measuring inter-particle forces in compressed hydrogels, but the full story is yet to come.