Gravitational Chu Limit and Gravitational Metamaterials
Gravitational Chu Limit
Recently, we have proposed a gravitational form of the electromagnetic Chu limit. The Chu limit is a 50-year old fundamental limit in electromagnetics that serves a central role in the design of small antennas. In our 2018 Phys Rev D article below, a simple formula is derived for the Q (quality factor) of gravitational radiation sources (gravitational antennas), similar to the Chu limit that sets bounds on the achievable Q governing the ratio of stored energy to radiated energy in the electromagnetic fields of antennas. Observed gravitational Q is plotted in the 2018 Phys Rev D article below, using recent measured gravitational-wave data for a gravitationally-small binary neutron star inspiral.
In Metamaterial Conference article below, notions of gravitational Q and gravitationally-small elements are used to describe prospective gravitational metamaterials. We explore inspiration from electromagnetic metamaterial frameworks where unit cells may be considered as electrically-small antennas. A gravitoelectromagnetic framework is used to explore a Veselago-inspired pathway to gravitational metamaterials. In an astrophysics context, interstellar distances are also shown to be less than a gravitational wavelength for certain planetary orbits.
- this PDF is © American Physical Society. (https://www.aps.org/):
Thomas P. Weldon, “Theoretical and observed quality factor of gravitational quadrupoles,” in Phys. Rev. D, vol. 98, p. 124044, Dec. 2018.
- Thomas P. Weldon and Kathryn L. Smith, “Gravitationally-Small Gravitational Antennas, the Chu Limit, and Exploration of Veselago-Inspired Notions of Gravitational Metamaterials,” in 13th International Congress on Artificial Materials for Novel Wave Phenomena – Metamaterials 2019 , Rome, Italy, Sep. 16-21, 2019.