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. (Also, see related new research on Gravitational metamaterials).

    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.

    The 2018 APS conference paper below shows the earliest preliminary results in our investigation of the gravitational form of the Chu limit.


  • this PDF is © American Physical Society. (
    Thomas P. Weldon, “Theoretical and observed quality factor of gravitational quadrupoles,” in Phys. Rev. D, vol. 98, p. 124044, Dec. 2018. APS weblink.
    (“Yes, the author or the author’s employer may use all or part of the APS published article, including the APS-prepared version (e.g., the PDF from the online journal) without revision or modification, on the author’s or employer’s website as long as a fee is not charged.”)
  • PDF preprint: Thomas P. Weldon, “Measured and Field-Based Theoretical Q of Gravitationally-Small Gravitational Antennas,” in 2018 IEEE International Symposium on Antennas and Propagation and USNC-URSI National Radio Science Meeting, Boston, MA, July 8-13, 2018.
  • PDF preprint: Christopher G. Daniel Jr., Kathryn L. Smith, and Thomas P. Weldon, “Observed Q and Gravitationally-Small Antenna Behavior of a Binary Black Hole Radiator,” in 2019 IEEE International Symposium on Antennas and Propagation (APSURSI), Atlanta, GA, July 7-12, 2019.