mini-workshop on "rheology of dense materials"

Wednesday Mar 18, 2026, 9:30 AM → 6:00 PM Asia/Tokyo

K206

We are pleased to announce a one-day Mini-Workshop on the Rheology of Dense Materials, to be held at the Yukawa Institute for Theoretical Physics, Kyoto University, on March 18, 2026. This meeting brings together an international group of researchers working on the physics of complex particulate and driven systems, spanning granular matter, active materials, nonequilibrium effects, and related theoretical frameworks. The workshop coincides with the visit of Professor Prabhu Nott (Indian Institute of Science), a leading expert in colloidal science.

Athermal particle systems — collections of macroscopic particles such as grains, sands, and suspensions that do not equilibrate thermally — exhibit rich rheological and dynamical behavior. Understanding and controlling these systems is a fundamental challenge with implications across physics, materials science, chemical and mechanical engineering, and geosciences.

The program features invited presentations that highlight current advances in both theory and experiment: 
Professor Prabhu Nott will share insights from his work in colloidal and particulate rheology.
We will discuss recent developments on the Mpemba effect — the counterintuitive phenomenon in which a system initially at a higher temperature can cool faster than one at a lower temperature under certain conditions.
One speaker will speak on the surface tension of active matter, exploring emergent interfacial phenomena in driven systems far from equilibrium.
Another speaker will present on the Ginzburg-Landau theory of dense granular matter, offering a theoretical perspective on collective behavior and structural transitions.
The other speaker will highlight her latest work on carrier dynamics in model superionic conductors, as detailed in her recent preprint on anharmonic and heterogeneous motion across sublattice melting.

This mini-workshop aims to foster interdisciplinary exchange and collaboration among participants working on a broad range of nonequilibrium and dense matter problems.

9:30 AM → 9:35 AM Opening address (Hisao Hayakawa, YITP, Kyoto Univ.)

9:35 AM → 10:05 AM Yue Liu (YITP, Kyoto Univ.) 30 min = 23 min talk + 7 min discussion

10:05 AM → 10:35 AM Frédéric van Wijland (CNRS & Univ. Paris Cité) "Wetting by active particles" (30 min = 23 min talk + 7 min discussion)

10:35 AM → 10:50 AM break

10:50 AM → 11:20 AM Satoshi Takada (TUAT) 30 min = 23 min talk + 7 min discussion

11:20 AM → 11:50 AM Michio Otsuki (Shimane Univ.) 30 min = 23 min talk + 7 min discussion

1:30 PM → 2:00 PM Harukuni Ikeda (YITP, Kyoto Univ.) 30 min = 23 min talk + 7 min discussion

2:00 PM → 2:15 PM Suravi Pal (Osaka Univ.) 15 min = 12 min talk + 3 min discussion

2:15 PM → 2:30 PM Sucharita Niyogi (Osaka Univ.) 15 min = 12 min talk + 3 min discussion

2:30 PM → 3:00 PM Takeshi Kawasaki (Osaka Univ.) 30 min = 23 min talk + 7 min discussion

3:00 PM → 3:15 PM break

3:15 PM → 3:45 PM Kuniyasu Saitoh (Kyoto Sangyo Univ.) 30 min = 23 min talk + 7 min discussion

3:45 PM → 4:05 PM Kota Noto (YITP, Kyoto Univ.) 20 min = 15 min talk + 5 min discussion

4:05 PM → 4:30 PM break

4:30 PM → 6:00 PM Prabhu Nott (Indian Institute of Science) "The mechanics of disordered granular media in statics and flow: biased random walks to jamming-yielding dynamics"

Disordered granular media, such as sand, mineral ores and food grains, exhibit features that are both solid-like and fluid-like. However, their mechanical response differs substantially from elastic solids and viscous fluids, due to the complexity of inter-grain interactions. In the static state, it is known that the stress depends strongly on how the grain assembly is created. In the flowing state, experiments show two contrasting rheological regimes, namely slow (quasistatic) and rapid (inertial) flow, for which the dependence of the stress on the shear rate are very different. We show that a combination of particle dynamics simulations and experiments throw light on the nature of stress transmission in static and flowing granular media, which lead to the development of closure or constitutive relations for the stress. We show that propagation of contact force in a static grain assembly under gravity can be thought of as a biased random walk. This helps us derive a simple closure relation for the macroscopic stress. For grains flowing in the slow flow regime, we show that deformation occurs via recurrent jamming-yielding dynamics, with the stress being elastic in the jammed phases and yielding occurring in short bursts. This findings lead to explanations for the rate independence of the stress and dilatancy, which are distinctive features of slow granular flow.