  The strongest bounds on some forms of Lorentz and CPT violation come from
astrophysical data, and placing such bounds may require understanding and
modeling distant sources of radiation. However, it is also desirable to have
bounds that do not rely on these kinds of detailed models. Bounds that do not
rely on any modeling of astrophysical objects may be derived both from
laboratory experiments and certain kinds of astrophysical observations. The
strongest such bounds on isotropic modifications of electron, positron, and
photon dispersion relations of the form E^2 = p^2 + m^ 2 + epsilon p^3 come
from data on cosmological birefringence, the absence of photon decay, and
radiation from lepton beams. The bounds range in strength from the 4 x 10^(-13)
to 6 x 10^(-33) (GeV)^(-1) levels.
