Abstract:
It has been recently suggested that structured media can bend light trajectories around an object, making it invisible, or even bending light the wrong way, making a flat lens convergent. Such electromagnetic metamaterials introduced by Sir John Pendry during the last decade have counterparts in acoustics [1], such as invisibility cloaks for surface water waves. In this talk, I will focus my attention on another type of surface waves: flexural (Lamb) waves propagating within thin elastic metamaterial plates which have been experimentally studied this year by research groups in Karlsruhe, Marseille and Paris. Interestingly, control of flexural waves opens a route towards seismic metamaterials. First experiments performed by multinational company Menard this year near the French cities of Grenoble and Lyon demonstrate that one can shield or even focus a seismic wave of magnitude 4 on the Richter scale through an array of meter sized holes drilled in a rather homogeneous soil. Finally, I will discuss some possible extension of the physics of metamaterials to thermodynamics. All of these metamaterials offer a nice playground for the high frequency homogenization (HFH) method, since much of the physics contained therein cannot be captured by classical homogenization theories in contrast with HFH.
[1] R. Craster, S. Guenneau, Acoustic Metamaterials: Negative refraction, imaging, lensing and cloaking, Springer Verlag, January 2013