Invisibility cloaks in relativistic motion

TL;DR

This paper analyzes how relativistic motion affects the effectiveness of ideal invisibility cloaks, revealing that motion generally causes detectability through distortions and spectral broadening, but certain conditions still allow perfect cloaking.

Contribution

It introduces the effects of relativistic motion on ideal cloaking, showing conditions where cloaking remains perfect and highlighting non-reciprocal behavior.

Findings

Moving cloaks become detectable via distortions and spectral broadening.

Ideal cloaking is possible under specific incident light and velocity conditions.

Cloaking becomes non-reciprocal, affecting light paths after reflection.

Abstract

We consider an ideal invisibility cloak which is illuminated by monochromatic light and which moves in vacuum at constant relativistic velocity with respect to the common inertial frame of light source and observer. We show that, in general, the moving cloak becomes detectable by image distortions and by generating a broad frequency spectrum of the scattered light. However, for many special combinations of incident light frequency, wave vector of light, and cloak velocity, ideal cloaking remains possible. It becomes non-reciprocal though. This means that light rays emitted by the light source arrive at the observer as though they have travelled through vacuum, but they take completely different paths after being retro-reflected at the observer position.