Einstein Was Right: Space-Time Is Smooth, Not Foamy

[bananas]

7. I think I found the abstract

http://adsabs.harvard.edu/abs/2013AAS...22115209N

Title: Limits on Cosmological Dispersion from Photon Bunches in GRB 090510 from Fermi LAT Data
Authors: Nemiroff, Robert J.; Connolly, R.; Kostinski, A.
Affiliation: AA(Michigan Technological Univ.), AB(Michigan Technological Univ.), AC(Michigan Technological Univ.)
Publication: American Astronomical Society, AAS Meeting #221, #152.09
Publication Date: 01/2013
Origin: AAS
Abstract Copyright: (c) 2013: American Astronomical Society
Bibliographic Code: 2013AAS...22115209N

Abstract

Three photons spanning about 30 GeV arrived within about one millisecond from the Fermi-detected GRB 090510A at a redshift of about 0.9. Although conceivably a > 3 sigma statistical fluctuation, when taken at face value, this photon bunch -- quite possibly a classic GRB pulse -- leads to a relatively tight bound on the ability of our universe to disperse high energy photons. Specifically given a generic dispersion relation where the time delay is proportional to the photon energy to the first power the limit on the dispersion strength is k1 < 1.61 x 10-5 sec Gpc-1 GeV-1. Two other short duration photon bunches bolster the statistical significance of this limit. In the context of some theories of quantum gravity this conservative bound translates into an minimum energy scale greater than 525 m_Planck suggesting that spacetime is smooth at energies perhaps a factor of 1000 below the Planck length.