Astrophysical Tests of Lorentz Symmetry in Electrodynamics
  In this talk presented at the Fourth International Workshop on New Worlds in Astroparticle Physics, I discuss recent constraints on Lorentz violation in electrodynamics. The observed absence of birefringence of light that has propagated over cosmological distances bounds some coefficients for Lorentz violation to 2 x 10^{-32}. 
Matthew Mewes