Gravitationally-Small Gravitational Antennas, the Chu Limit, and Exploration of Veselago-Inspired Notions of Gravitational Metamaterials

Recent results provide an analytic expression for the quality factor, or Q, of gravitationally-small gravitational quadrupoles, drawing upon similarities to the Chu limit for electrically-small electromagnetic antennas. Thus, in some sense gravitationally-coupled systems are similar to metamaterials, having high-Q resonant elements separated by much less than a wavelength, and supporting gravitational wave propagation through the resonant elements. These new results raise the question of whether the notions of gravitational Q and gravitationally-small elements may lead to insights for the development of gravitational meta-materials. Here, we review recent gravitational Q results, and explore potential inspiration from electromagnetic metamaterial frameworks where unit cells may be considered as electrically-small antennas. Finally, a gravitoelectromagnetic framework is used to explore a Veselago-inspired approach to hypothetical gravitational metamaterials, should a gravitational unit cell be found. In an astrophysics context, interstellar distances are also shown to be less than a gravitational wavelength for certain planetary orbits.