Elastic wavepackets crossing a space-time interface

TL;DR

This paper experimentally studies elastic wave packets crossing a dynamic space-time interface in a stretched elastic strip, revealing non-conservation of wavelength and frequency and confirming theoretical predictions of wave shifts.

Contribution

It introduces a novel experimental setup to create and analyze a moving elastic interface, demonstrating wave behavior consistent with theoretical models in dynamic media.

Findings

Wave packets experience wavelength and frequency shifts at the moving interface

The experimental results confirm theoretical predictions of wave behavior in dynamic media

Dynamic stretching creates a controllable space-time interface in elastic media

Abstract

The interaction between waves and evolving media challenges traditional conservation laws. We experimentally investigate the behavior of elastic wave packets crossing a moving interface that separates two media with distinct propagation properties, observing the non-conservation of wavelength and frequency. Our experimental setup employs an elastic strip whose local stretching can be dynamically altered by pulling one end at a constant velocity. By demonstrating that this dynamic configuration creates a spatio-temporal interface traveling along the strip, we confirm theoretical predictions regarding observed shifts when a wave packet crosses this interface.