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Accueil du site > Seminars > Séminaires théorie > MSC seminar on Monday, March 28th, 2022. Elisabeth Agoritsas: "Role of structural disorder in dense particle systems: from amorphous materials to active matter.".

MSC seminar on Monday, March 28th, 2022. Elisabeth Agoritsas: "Role of structural disorder in dense particle systems: from amorphous materials to active matter."

Unless otherwise stated, seminars and defences take place at 11:30 in room 454A of Condorcet building.


Speaker: Elisabeth Agoritsas (EPFL, Switzerland)

Title: Role of structural disorder in dense particle systems: from amorphous materials to active matter

Abstract: Disorder is ubiquitous in physical systems, and can radically alter their physical properties compared to their ‘pure’ counterparts. For instance, ferromagnetic materials can be used as magnetic memories in our computers’ hard drives only because of the presence of impurities in their crystalline structure: the latter allows for the ‘pinning’ of the ferromagnetic domain walls between digital bits, and the resulting stability of these memories. A very large class of systems lies on the opposite limit where there is no crystalline structure to start from at all: emulsions as mayonnaise, foams, or metallic glasses are all structurally disordered, and this has key implications for their rheological, mechanical, or transport properties.

There have 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 two studies performed in that spirit, at a mean-field level. In [1,2], we compared the mechanical response between sheared granular material and active matter, in the glassy phase where they behave as ’solids’. 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 [3] we examined how the activity stemming from the apoptosis and division rate in a model biological tissue can on the contrary fluidise these materials, resulting in the non-linear rheology of a ‘complex fluid’.

[1] "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).

[2] "Mean-field dynamics of infinite-dimensional particle systems: global shear versus random local forcing",E. Agoritsas, J. Stat. Mech. 2021, 033501 (2021).

[3] "Nonlinear Rheology in a Model Biological Tissue", D. A. Matoz-Fernandez*, E. Agoritsas*, J.-L. Barrat, E. Bertin, and K. Martens, Phys. Rev. Lett 118, 158105 (2017).


Contact : Équipe séminaires / Seminar team - Published on / Publié le 29 March


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