Mesoscale modelling of driven disordered materials: from glasses to active matter
CECAM-HQ-EPFL, Lausanne, Switzerland
Deadline for registration and abstract submission:
A limited number of slots will be available for contributed talks, poster presentations, and participation (max. around 50). Upon registration, researchers interested in giving such a contributed talk and/or presenting a poster are invited to submit an abstract through the workshop website, before March 11, 2023. We will primarily select participants from those who submit the abstract. Please note that the selection for the confirmed participants and the abstracts will be notified on March 18, 2023.
- March 11, 2023: Deadline for registration and abstract submission
- March 18, 2023: Notification on contributed talks and posters
- May 24-26, 2023: CECAM Workshop at EPFL, Lausanne, Switzerland
Amorphous materials are ubiquitous around us, encompassing for instance colloids, emulsions, foams, granular matter and metallic glasses, as well as confluent biological tissues. These materials are seemingly very different from each other, as the size of their constituent particles ranges from nanometers (e.g. metallic glasses) to millimeters (e.g. grains) with very dissimilar particle interactions. Nevertheless, they exhibit common features under external forces or self-propulsion, showing universal non-equilibrium behaviours such as localised plastic rearrangements, collective or avalanche-type motion, or the emergence of shear bands. These remarkable observations naturally led researchers to search for a unified description of driven amorphous materials, particularly at a mesoscopic scale where microscopic details become irrelevant [1,2].
It is now well established that the mechanical response of amorphous solids under loading proceeds from local and irreversible rearrangements, resetting disorder locally and generating a highly non-trivial mechanical noise [1,2]. These plastic events were first identified by Argon  and later on coined as shear transformation zones (STZs) . They play a central role in mechanical and rheological properties, providing us with the key building blocks for various theoretical descriptions, such as STZ theory  and elasto-plastic models (EPMs) . The development of these effective descriptions has been tightly related to advances on other non-equilibrium statistical physics phenomena, such as the depinning transition [5,6] and ferromagnets in random fields . Recent advances in stochastic processes, such as random resetting, could provide useful theoretical tools to refine these descriptions . In this context, understanding the nature of the noise and the characterisation of local disorder is becoming one of the forefront of numerous works, particularly for dense active matter  where classical equilibrium concepts are challenged.
On the numerical front, spatio-temporal scales accessible by molecular dynamics are limited. Thus atomistic simulations have been complemented by discrete mesoscopic approaches, allowing to reproduce the response of driven amorphous materials while considerably reducing the number of degrees of freedom to be processed . EPMs consider a discrete population of STZs triggered in an elastic medium, and can be seen as a mechanical analogue of an Ising model where local plastic deformation and elastic propagator correspond respectively to spin and interaction between the sites. Many versions of coarse-grained, mesoscopic modellings with different ingredients have been devised to investigate the collective organisation of STZs, either spatially-resolved [2,10] or effectively mean-field , to explore various mechanisms (e.g. avalanches, shear bands ) and rheological settings (e.g. stationary, transient regimes, oscillatory protocols [13,14]). Furthermore, recent studies focused on the detailed calibration of these mesoscopic models using microscopic information obtained by molecular simulations [16,17]. This multiscale-modelling approach, mapping from molecular simulations to mesoscopic models, paves the way to construct more realistic modelling, also by applying them to experimental systems such as colloids and granular materials [18,19]. Such mesoscopic modelling is also becoming paramount for dense active matter, by relying on connections with driven yet passive amorphous materials within a unified framework .
Misaki Ozawa (University of Grenoble Alpes) - Organiser
Sylvain Patinet (CNRS ESPCI) - Organiser
Elisabeth Agoritsas (University of Geneva) - Organiser