  Lorentz symmetry violation (LSV) at Planck scale can be tested (see e.g.
physics/0003080) through ultra-high energy cosmic rays (UHECR). In a deformed
Lorentz symmetry (DLS) pattern where the effective LSV parameter varies like
the square of the momentum scale (quadratically deformed relativistic
kinematics, QDRK), a 10E-6 LSV at Planck scale would be enough to produce
observable effects on the properties of cosmic rays at the 10E20 eV scale:
absence of GZK cutoff, stability of unstable particles, lower interaction
rates, kinematical failure of any parton model and of standard formulae for
Lorentz contraction and time dilation... Its phenomenological implications are
compatible with existing data. If the effective LSV parameter is taken to vary
linearly with the momentum scale (linearly deformed relativistic kinematics,
LDRK), a LSV at Planck scale larger than 10E-7 eV seems to lead to
contradictions with data above TeV energies. Consequences are important for
high-energy gamma-ray experiments, as well as for high-energy cosmic rays and
gravitational waves.
