Astrophysical Searches for Quantum Gravity Signals

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Some recent searches for quantum gravity signatures using
observations of distant astrophysical sources will be discussed, focusing on
the search for Lorentz invariance violation (LIV) in the form of a dependence
of the photon propagation speed on its energy. Fermi gamma-ray space telescope
observations of ~8 keV to ~30 GeV photons from a short ( burst (GRB 090510) at a cosmological distance (z = 0.903), enabled for the
first time to put a direct time of flight limit on a possible linear variation of
the speed of light with photon energy that is beyond the Planck scale.

|v/c-1| = E/E_{QG} our most conservative limits are

> 1.2, while less conservative limits are up to 1-2
orders of

magnitude stricter. Other types of astrophysical searches
for LIV will be briefly outlined, along with some prospects for the future.