Programme > Contributed presentations

Ettore Angeli — Pinning Dominated Dynamics and Internal Texture Effects in Field- and Spin-Orbit Torque-Driven Domain Walls

Eric Bertin — Giant density fluctuations in locally hyperuniform states

Satyanu Bhadra — Deflatables

Oscar Bouverot-Dupuis — One-dimensional dissipative Mott transition

Pierre-Yves Corbel —  Kinematics of an elastic fiber dragged in a granular medium

Jérôme Crassous — Knots

Caroline Crauste-Thibierge —  Memory effects at small and large strain in polymer films

Thorsten Emig — How far does shear propagate? Boundary-driven granular flow in channels with complex basal forcing

Antoine Faulconnier — Laddering in knitted fabrics

Thierry Giamarchi — Disorder and interactions in one-dimensional quantum system

Hervé Henry — Phase field study of fracture in heterogeneous materials

Valentin Lallemant — An explicit formula of the Oslo stationary state

Laura Michel — Mechanics of a model knitted fabric

Giacomo Morpurgo — Localization Transition for Interacting Quantum Particles in Colored-Noise Disorder

Baptiste Parage — Interplay between activity and attraction in active polymers

Anshul Parmar — Tuning dynamics and mechanics of disordered systems via structural constraints

Alice Pelosse — How drop volume and particle size shape evaporating armored droplets

Solenn Rodriguez — Mechanical Behaviour of Confined Ferromagnetic Granular Materials

Chatterjee Roni — Memory behavior of a randomly driven model glass

Giovanni Russo — Creep Motion of Amorphous Solids

Stéphane Santucci — Multiscale stress dynamics in sheared liquid foams revealed by tomo-rheoscopy

Anne Tanguy — Disorder and Non-Linear interactions

Ptashanna Thiraux — Exploring and simulating earthquake interactions

Loic Vanel — Rupture of heterogeneous materials: Creep and stress relaxation dynamics? or Time-dependent sideways cracks in filled elastomers?

Maud Viallet — Discharge of magnetic particles in a 2D silo

Wiese Kay — How can zeta = 1.25 for an elastic string at depinning be realized in an experiment?

Zetterberg Love — Creep vs relaxation in brittle disordered solids

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Ettore Angeli — Pinning Dominated Dynamics and Internal Texture Effects in Field- and Spin-Orbit Torque-Driven Domain Walls

TBA.

Eric Bertin — Giant density fluctuations in locally hyperuniform states

Systems driven far from equilibrium may exhibit anomalous density fluctuations: active matter with orientational order display giant density fluctuations at large scale, while systems of interacting particles close to an absorbing phase transition may exhibit hyperuniformity, suppressing large-scale density fluctuations. We show that these seemingly incompatible phenomena can coexist in nematically ordered active systems, provided activity is conditioned to particle contacts. We characterize this unusual state of matter and unravel the underlying mechanisms simultaneously leading to spatially enhanced (on large length scales) and suppressed (on intermediate length scales) density fluctuations. Our work highlights the potential for a rich phenomenology in active matter systems in which particles' activity is triggered by their local environment, and calls for a more systematic exploration of absorbing phase transitions in orientationally-ordered particle systems.

Satyanu Bhadra — Deflatables

We present a new method of shape transformation via application of vacuum over 3d printed TPU structures enclosed in a fabric. This method allows us to print 3d structures with double curvatures which are flat until activated. This allows for easier storage and transport, rapid deployment , and dissassembly when finished. We will go over the various steps of the process, starting from a target 3d shape to the final assembly and deployment.

Oscar Bouverot-Dupuis — One-dimensional dissipative Mott transition

We establish the full phase diagram of a 1D bosonic system coupled to local baths acting as dissipation. We identify three phases: a Luttinger liquid (LL), a Mott insulator (MI) and, in between, a dissipative phase (DP). Using state-of-the-art Monte Carlo simulations, we confirm that the LL/DP transition lies in the BKT universality class, and, for the first time, characterize the universality class of the MI/DP transition. The critical exponents are shown to be $z=4$ and $\nu=1/4$.

Pierre-Yves Corbel —  Kinematics of an elastic fiber dragged in a granular medium

How an elastic rod deforms within a dense granular medium is a complex fluid–structure interaction problem. Quantifying the forces required to insert or extract a rod from the granular medium, as well as understanding how the rod deforms and displaces the surrounding grains, are both fundamental and technological questions. These issues arise in applied fields such as the mechanical reinforcement of materials with fibers or fiber separation–extraction processes in the recycling of fibrous materials. They are also relevant in several areas of biology, from the swimming of sandfish to the uprooting of plant roots from soil. To identify the purely mechanical behavior of this fluid–structure interaction, we designed an experiment in which a fiber of variable shape is dragged through a two-dimensional granular medium confined within a horizontal cell under an imposed pressure. The relevant scale for our study is that of the grain, to understand the coupling between the fiber elasticity and the discrete nature of the granular medium. We present initial results on the conformational changes of an elastic fiber with an initially sinusoidal shape, as a function of the fiber's geometric and mechanical parameters, and for several imposed confinement pressures in the granular medium. In particular, we investigated the rectification of the fiber (change in amplitude) as a function of its length, thickness, initial wavelength, and initial amplitude of the sinusoidal shape. Based on the results obtained for rectification, we propose a renormalization law derived from the deflection of a beam under distributed loading.

Jérôme Crassous — Knots

I will present some recent results on the effect of friction on the mechanical stability of knots. By combining numerical modeling and theoretical analysis, we will show that knots (within the limits of flexible rope) can be viewed as a mechanical feedback mechanism for tension between different points on the rope.

Caroline Crauste-Thibierge —  Memory effects at small and large strain in polymer films

Memory is a well-known property of disordered systems. Usually, their answer to a perturbation depends not only on the perturbation itself but also of the thermal or mechanical history of the material. Submitted to mecanical strain (or shear), they can keep in their structure the signature of the direction or of amplitude of the strain. Under certain conditions, it becomes possible to read this memory of the mechanical history. Using a tensile machine, we apply strain to polymer films and measure their mechanical response. We also perform in-situ dielectric measurements during the strain. I will present our last results on different kinds of memory effects including Baüchinger effects in two limit regims of the polymer response. We studied the low strain response, in the reversible plastic regim and the high strain response in the stran-hardening regim in polycarbonate sheets.

Thorsten Emig — How far does shear propagate? Boundary-driven granular flow in channels with complex basal forcing

We investigate slow, dense granular flows in a channel driven by prescribed basal motion, motivated by split-bottom and boundary-driven shear experiments. Using a regularized viscoplastic formulation inspired by the μ(I) rheology, we compute steady velocity fields in a U-shaped channel with rough sidewalls and various basal forcing profiles, including uniform, split, and sinusoidal motion. A robust geometric control of shear penetration emerges: the surface velocity drops sharply once the filling height exceeds a lateral length scale set by the width or wavelength of the basal forcing. When expressed in terms of an effective aspect ratio, the transition occurs for values of order unity and is largely independent of driving speed in the quasi-static regime. This approach provides a simple framework to study boundary-driven granular flows without explicitly tracking yield surfaces, and naturally extends to the full μ(I) rheology and to models including normal-stress effects relevant for non-spherical grains.

Antoine Faulconnier — Laddering in knitted fabrics

A knitted fabric is composed of a series of loops, called stitches, which are intertwined from a single thread. This network of loops is stabilized by its topology. Knits are all at once highly flexible, stretchable, lightweight, and strong. These remarkable mechanical properties emerge from their architecture, controlled by the deformation of the loops on one hand and solid friction at the thread crossings on the other. In this sense, the knitted fabric can be classified in the category of metamaterials. In such system, a local break of the thread within the fabric generates a topological defect within the stitches network that is able to propagate along the stitches columns at high velocity. This phenomenon, known as laddering, is the primary cause of failure in tights. However, in practice, while sometimes the defect are able to propagate across the whole fabric, it sometimes also can stop, slow down, restart, or even not propagate at all. Therefore, in this work, we aim at understanding what governs this complex behaviour. For this, in the framework of the ANR FiScal, we have conducted series of experiment relying on a biaxial tensile test machine to adress this question. To begin with, we will describe the laddering phenomenon. Then we will question the influence of some key parameters, such as the tension and knit geometry, offering insights into the mechanisms behind ladder propagation in knitted fabrics.

Thierry Giamarchi — Disorder and interactions in one-dimensional quantum system

TBA.

Hervé Henry — Phase field study of fracture in heterogeneous materials

I will discuss if it is possible to describe crack propagation in heterogeneous materials using effective laws for propagation that average material properties over a representative volume. The discussion will be based on numerical simulations using phase field models.

Valentin Lallemant — An explicit formula of the Oslo stationary state

TBA.

Laura Michel — Mechanics of a model knitted fabric

Knitted fabrics consist of yarns intertwined into an intricate periodic network of loops. The mechanical response of such a network is inherently nonlinear, dissipative, and history-dependent, due to the slenderness of the fibers and the frictional contacts between threads. As a result, predicting the mechanical response of a fabric remains an ongoing challenge, even numerically. In this work, we describe the elasticity of periodic frictional knitted fabrics using both a 2D elastica model and a 3D numerical model. In particular, we show that, in the absence of solid friction between threads, the mechanics of the fabrics can be fully rationalized through the study of their elastic energy. When solid friction between threads is taken into account, one can still determine the possible equilibrium shapes for a given set of applied forces or, conversely, the possible applied forces for a given shape. Finally, we show that a simple model allows to predict the spontaneous curvature of such fabrics.

Giacomo Morpurgo — Localization Transition for Interacting Quantum Particles in Colored-Noise Disorder

We investigate the localization transition of interacting particles in a one-dimensional correlated disorder system. The disorder which we investigate allows for vanishing backwards scattering processes. We derive by two renormalization group procedures its phase diagram and predict that the localization transition point is shifted from finite attractive interaction to the non-interacting point. We finally show numerically that the scaling of the localization length with the disorder strength deviates from the usual scaling of a localized phase.

Baptiste Parage — Interplay between activity and attraction in active polymers

Among the exciting classes of active matter, self-propelled polymer-like objects are particularly notable for their relevance across biological systems, from cytoplasmic biopolymer networks to worm collectives at the macroscopic scale. While activity is known to strongly affect the conformation and dynamics of self-repelling chains, generally leading to chain shrinkage, its impact on the attraction-driven coil-to-globule transition remains largely unexplored. We address this question by performing single-chain Brownian dynamics simulations of three-dimensional flexible, tangentially driven active polymers with intrachain attraction. We find that activity smears out the collapse transition, promoting necklace-like conformations before the polymer forms a highly reconfigurable compact globule. Interestingly, the effect of activity varies with attraction strength, leading to activity-induced shrinkage below the theta point and swelling above it. By rescaling the attraction strength into an effective activity-dependent parameter, we obtain a universal master curve for the radius of gyration.

Anshul Parmar — Tuning dynamics and mechanics of disordered systems via structural constraints

Structural engineering of disordered systems and tuning their properties remain central challenges in materials science. We present a model of gel-like particles connected by reversible bonds, where bond strength and concentration directly determine the material's physical properties. Simulations show that varying these parameters produces dramatic changes in structural relaxation, thermal stability, and mechanical response. Bond strength and concentration also enable long-lived yet reconfigurable states, linking microscopic bonding dynamics to macroscopic performance. This framework provides a versatile route to design disordered materials with tailored properties.

Alice Pelosse — How drop volume and particle size shape evaporating armored droplets

When a drop evaporates, its shape is dictated by capillarity. However, for liquid marbles, i.e., drops coated with hydrophobic particles trapped at the interface, the situation is fundamentally different. The particulate shell must then adapt to a shrinking volume while balancing the solid-like mechanical properties of the interface. In this talk, I will demonstrate how elasticity features emerge in such discrete armor by systematically varying both the drop volume and the particle size in experiments. I will also show how the initially disordered particle arrangement evolves under compression into crystalline structures with defects, defects that ultimately govern the drop's deformation. This interplay between volume reduction, particle size, and structural organization reveals the singular mechanics of armored drops.

Solenn Rodriguez — Mechanical Behaviour of Confined Ferromagnetic Granular Materials

The pressure at the bottom of a container filled with granular material saturates [1], as the silo walls can support part of the grains' weight due to frictional interactions — a phenomenon known as the “Janssen Effect.” We investigate this effect using ferromagnetic particles: when exposed to a magnetic field, these particles acquire a magnetic moment, leading to anisotropic magnetic interactions. We develop different experimental setups and Discrete Element Method (DEM) simulations [2], in both 3D and 2D. We demonstrated recently that applying a magnetic field aligned with the granular column results in an even greater reduction of the pressure at the bottom of the container [3] compared to the classical Janssen Effect. Strikingly, beyond a critical magnetic field or a critical mass of grains, the apparent weight of the column can be completely canceled, rendering the column undetectable on the scale! We focus on the approach of the “invisibility” threshold, examining the impact of the magnetic field intensity and the initial mass of grains. We also studied the influence of the proportion of ferromagnetic grains within the column: the pressure at the bottom of the column decreases only when the fraction of magnetic grains exceeds a threshold corresponding to the percolation of magnetic clusters [4]. [1] Janssen, H. A. Investigations of pressure of grain in silo. Vereins Eutscher Ingenieure Zeitschrift 1045-1049 (1895). [2] J. Sautel, C.E. Lecomte, N. Taberlet, Particle size segregation in two-dimensional circular granular aggregates. Physical Review E, 103(2), 022901 (2021). [3] L. Thorens, K.J. Måløy, M. Bourgoin, S. Santucci, Magnetic Janssen effect, Nature Comm., 12, 2486 (2021). [4] L. Thorens, S. Rodriguez, N. Taberlet, M. Bourgoin, K.J. Måløy, S. Santucci, Hybrid Magnetic Janssen Effect Arising from Percolating Ferromagnetic Grain Networks, submitted 2026.

Chatterjee Roni — Memory behavior of a randomly driven model glass

We investigate by atomistic simulations the memory behavior a model glass subjected to random driving protocols. The training consists of a random walk of forward and/or backward shearing sequences bounded by a maximal shear strain of absolute value γT . We show that such a stochastic training protocol is able to record the training amplitude. Different read-out protocols are also tested and are shown to be able to retrieve the training amplitude. We then emphasize the ten- sorial character of the memory encoded in the glass sample and then characterize the anisotropic mechanical behavior of the trained samples.

Giovanni Russo — Creep Motion of Amorphous Solids

TBA.

Stéphane Santucci — Multiscale stress dynamics in sheared liquid foams revealed by tomo-rheoscopy

Rheology aims at quantifying the response of materials to mechanical forcing. However, standard rheometers provide only global macroscopic quantities, such as viscoelastic moduli. They fail to capture the heterogeneous flow of soft amorphous materials at the mesoscopic scale, arising from the rearrangements of the microstructural elements, that must be accounted for to build predictive models. To address this experimental challenge, we have combined shear rheometry and time-resolved X-ray micro-tomography on 3D liquid foams used as model soft jammed materials, yielding a unique access to the stresses and contact network topology at the bubble scale. We reveal a universal scaling behavior of the local stress build-up and relaxation associated with topological modifications. Moreover, these plastic events redistribute stress non-locally, as if the foam were an elastic medium subjected to a quadrupolar deformation. Our findings clarify how the macroscopic elastoplastic behavior of amorphous materials emerges from the spatiotemporal stress variations induced by microstructural rearrangements.

Anne Tanguy — Disorder and Non-Linear interactions

In this talk, I would like to compare different signatures of non-linear interactions in disordered materials like amorphous solids: spatial dependence of group velocity and non-linear waves, localization of low frequency waves, plasticity. We will discuss possible effects on thermal transfer, when disorder is at the atomic scale.

Ptashanna Thiraux — Exploring and simulating earthquake interactions

Earthquakes and faults are often considered a paradigm of “crackling noise,” i.e., slowly driven complex systems that respond through intermittent events [1], characterized by scale-free statistics such as a power-law distribution of seismic moments (the Gutenberg-Richter law), and space/time correlations expressed, for example, by a slowly decaying rate of aftershocks (Omori's law) associated with scale-free (sub)diffusion. Understanding the physical origin of these scaling laws is of primary importance for natural hazard forecasting. Slider-block models, incorporating only simple static friction and elastic interactions, have long been proposed to simulate fault mechanics and earthquakes [2]. The seminal 1D models were later extended to 2D using cellular automata with a simplified, short-range version of elastic stress redistribution [3]. While these models can simulate intermittent events with power-law-distributed slip sizes, they lack a timescale and thus cannot simulate aftershocks or the associated space and time clustering. More recently, deterministic rheologies (e.g., viscoelastic [4] or rate-and-state [5]) have been introduced to capture these complex space/time properties. We introduce timescales at a more fundamental level by incorporating thermal activation [6] of individual block slip. This approach allows exploration of the coupled effects of thermal activation and elastic stress redistribution on earthquake self-organization, as well as the influence of temperature on earthquake triggering. Additionally, the impact of the elastic redistribution kernel—short-range versus more realistic long-range—is investigated. The introduction of healing processes enables modeling of both velocity-strengthening and velocity-weakening regimes in the rate-and-state framework, without adding deterministic rheologies. Another improvement is computing real slip in a dislocation-like model to simulate earthquakes, and further study the link between stress field correlations, the Gutenberg-Richter exponent, and cutoff is in progress. Refs. : [1] J. P. Sethna, K. A. Dahmen, and C. R. Myers, *Nature* **410**, 242 (2001). [2] R. Burridge and L. Knopoff, *Bulletin of the Seismological Society of America* **57**, 341 (1967). [3] Z. Olami, H. J. S. Feder, and K. Christensen, *Phys. Rev. Lett.* **68**, 1244 (1992). [4] E. Jagla and A. Kolton, *Journal of Geophysical Research: Solid Earth* **115** (2010). [5] T. W. de Geus and M. Wyart, *Phys. Rev. E* **106**, 065001 (2022). [6] J. Weiss *et al.* (2025) *In prep.

Loic Vanel — Rupture of heterogeneous materials: Creep and stress relaxation dynamics? or Time-dependent sideways cracks in filled elastomers?

TBA.

Maud Viallet — Discharge of magnetic particles in a 2D silo

We study the impact of magnetic interactions induced by an external magnetic field on the discharge of a 2D hourglass filled with a mono-layer of ferromagnetic grains. We demonstrate control of the granular flow via an effective tunable friction with the cell walls that increases with the amplitude of the applied magnetic field, and modifies the velocity profiles at the aperture, up to the emergence of a jamming transition.

Wiese Kay — How can zeta = 1.25 for an elastic string at depinning be realized in an experiment?

TBA.

Zetterberg Love — Creep vs relaxation in brittle disordered solids

When studying materials that are subjected to loading over long periods of time, two phenomena, creep and stress relaxation, emerge as a sort of mirror image of one another. Creep is defined as the slow deformation of a material under constant load, while relaxation is defined as a material held at constant strain and displaying a slow decrease of the internal stress. In the case of brittle heterogenous materials, which are of great importance for example in civil engineering and rock mechanics, these two phenomena can be linked to thermally activated microfracturing. Strain evolution during creep strain is typically modelled in three stages, starting with a primary slowing down of the strain rate, a possible secondary creep associated to a constant strain-rate preceding an acceleration to macroscopic failure. Primary creep is most commonly modelled as a power law decrease of the strain rate with time. Similarly, relaxation is often observed as a logarithmic decrease of the stress with time, corresponding to a stress-rate decaying as 1/t. In both cases these descriptions remain phenomenological and do not explain the underlying process . Modelling the material as a collection of subvolumes, each capable of deforming and damaging once a local “yield” stress is reached athermally, or by thermal activation, one can create more physically grounded models for creep and relaxation of disordered brittle materials. A 1st order approach, analytically tractable, is to describe primary creep from a statistical exhaustion model, assuming thermal activation of individual subvolume damage, but ignoring elastic stress redistribution . However, this idealized approach neglects spatially and temporally localized effects which have been shown to increase the strain rate and decrease the time to failure through internal stress redistribution. In order to better understand the relationship between primary creep and relaxation in brittle materials, and aiming to clarify the relationship between these two macroscopic phenomena and the significance of internal stress redistributions for the underlying microscopic damaging, we analyze creep as well as relaxation tests performed on concrete samples, and in particular acoustic emissions furnishing a precise chronology of damage events. This is compared to what is expected from a simple exhaustion model in order to reveal the combined role of quenched disorder, thermal activation and elastic stress redistributions on these processes.