Coming up next
2025-04-03 - 13:30 @ New Gorlaeus DM1.19
SLAM seminar: Yoav Lahini (Martin's guest)
Title: Memory and aging via frustrated instabilities: from crumpled sheets to seismic aftershocks
Abstract: Understanding the unusual yet seemingly universal dynamics of disordered systems trapped far from equilibrium remains a major challenge. Yet, they are not very hard to observe. Take, for example, a thin plastic sheet and crumple it into a ball. It might not be immediately evident, but this seemingly mundane object exhibits many of the hallmark behaviors shared by complex non-equilibrium and disordered systems. These include logarithmic aging spanning many timescales, intermittent mechanical responses, crackling noise, avalanche dynamics, and a range of memory effects. Using experiments that combine global mechanical measurements, local probing, acoustic measurements, and 3D imaging of crumpled sheets, we build a mesoscopic description of their mechanics. These reveal that both memory and aging behaviors emerge from the collective dynamics of mesoscopic, bistable elements within the sheet: localized geometric instabilities that act as coupled, hysteretic, two-state degrees of freedom.
Based on this picture, we develop a numerical model of a disordered network of bistable elastic elements that corroborates all our findings: intermittencies, memory formation, aging, and avalanches. The model highlights the role of interactions and frustration between instabilities in driving these behaviors. The emerging picture is of a disordered system with a complex energy landscape, reminiscent of a mechanical spin-glass, that self-organizes to a state which lies on the edge of stability.
Applying our analysis to the temporal dynamics of seismic aftershocks reveals strikingly similar results, suggesting that a similar physical mechanism underlies aftershock dynamics and the celebrated phenomenology of Omori’s law.
Read more here:
Memory from coupled instabilities in unfolded crumpled sheets, PNAS (2022), https://www.pnas.org/doi/10.1073/pnas.2200028119
Logarithmic aging via instability cascades in disordered systems, Nature Physics (2023), https://www.nature.com/articles/s41567-023-02220-2