Wave control and frustration in space-time varying media
| When |
Jan 12, 2026
from 11:00 to 12:00 |
|---|---|
| Where | Salle Condorcet |
| Contact Name | Alexis Poncet |
| Attendees |
Benjamin Apffel |
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Propagation of waves can be strongly impacted by the spatial properties of the propagating media, leading to focusing, guiding or diffusion. However, quantities such as frequency or energy remain conserved along those processes due to time-invariance of the system. This constrain is relaxed in so-called « time-varying media », which temporal variation offers new control possibilities such as frequency conversion or amplification. In the first part of this talk, an experimental implementation of spatial and temporal control of water waves using electrostriction will be presented. This original manipulation technique offers contactless, tunable control both in space and time with excellent accuracy. The versatility of the proposed experiment will also be used to implement spatio-temporal control, resulting in enhanced wave control compared to purely spatial or temporal media.
In a second part, I will discuss the emergence of frustration in a space-time varying media, namely the inability for dynamical variables to all fulfil local order condition due to global spatio-temporal constrains. The experimental system consist in a coupled parametric oscillators pumped by a propagating wave,such that each oscillator experiences a different phase pump. By carefully choosing the wavelength of the pump, a phase dislocation must appear between adjacent oscillators. I will show that this dislocation travels across the whole media at constant velocity, that is characterized experimentally. Differences with standard geometrical frustration in Ising chain, as well as consequences of frustration propagation on the ergodicity of the system, will also be emphasized.