Astrophysical Limit on the Deformation of the Poincare Group
The deformed Poincaré group contains a characteristic mass, $κ$. At energies exceeding $κ$, deviations from the special theory of relativity become significant. However, small deviations from ordinary relativistic kinematics are observable even at energies substantially lower than $κ$. The observation of distant events producing ultra high energy (UHE) particles leads to a lower limit on $κ$. From an analysis of the UHE data on the burst in the binary system HER X1 in 1986, we deduce $κ> 1.3 10^{12}$~GeV.
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