Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Domaines cond-mat.stat-mech
Date Mercredi 23 Mars 2022
Heure 14:30
Institut LPENS
Salle Salle Djebar (29 rue d'Ulm)
Nom de l'orateur Agoritsas
Prenom de l'orateur Elisabeth
Addresse email de l'orateur
Institution de l'orateur EPFL
Titre Role of structural disorder in dense particle systems: from amorphous materials to active matter
Résumé Amorphous materials are ubiquitous around us: emulsions as mayonnaise, foams, sandpiles or biological tissues are all structurally disordered, and this has key implications for their response to an external deformation. Nevertheless, theoretical descriptions of such ‘driven' amorphous materials remain challenging, despite of decades of extensive analytical and computational studies. The difficulties pertain to the interplay of competing sources of stochasticity, and to the resulting out-of-equilibrium nature of these systems. A standard model for amorphous materials, which allows to focus on the key role of their structural (positional) disorder, is provided by dense many-body systems of pairwise interacting particles. In infinite dimension, these systems even provide exact analytical benchmarks for quasistatic features of amorphous materials, such as their response under quasistatic shear. Furthermore, there has been recently many attempts to relate the important corpus of known results for such ‘passive' amorphous materials, and their counterparts in active matter such as confluent biological tissues. One strong motivation is that the interplay between activity and structural disorder might in turn be related to biological functionalities. Here I will discuss recent results on the exact mean-field dynamics of these many-body systems, that we have derived in the limit of infinite spatial dimension, for different driving protocols. We were in particular able to establish a direct equivalence between a global forcing (external shear) and a random local forcing (reminiscent of active matter), upon a simple rescaling of the control parameter (the accumulated strain). In this framework, global shear is thus simply a special case of a much broader family of local forcing, that can be explored by tuning its spatial correlations. Our predictions were moreover found to be in remarkably good agreement with two-dimensional numerical simulations. These results hint at a unifying framework for establishing rigorous analogies, at the mean-field level, between different families driven disordered systems, such as sheared granular materials and active matter. [1] "Out-of-equilibrium dynamical equations of infinite-dimensional particle systems I. The isotropic case", E. Agoritsas, T. Maimbourg and F. Zamponi, J. Phys. A: Math. and Theor. 52, 144002 (2019). [2] "Out-of-equilibrium dynamical equations of infinite-dimensional particle systems. II. The anisotropic case under shear strain", E. Agoritsas, T. Maimbourg and F. Zamponi, J. Phys. A: Math. and Theor. 52, 334001 (2019). [3] "A direct link between active matter and sheared granular systems », P. Morse*, S. Roy*, E. Agoritsas*, E. Stanifer, E. I. Corwin, and M. L. Manning, PNAS 118, e2019909118 (2021). [4] "Mean-field dynamics of infinite-dimensional particle systems: global shear versus random local forcing », E. Agoritsas, J. Stat. Mech. 2021, 033501 (2021)
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