Comment on “Testing Planck-Scale Gravity with Accelerators”

Figure 1

Regions of allowed energies for an electron and a photon in the vacuum Cherenkov radiation at $n-1=1.4\times {10}^{-9}$, $1.7\times {10}^{-11}$, $10^{-12}$, $4.1\times {10}^{-13}$ (from left to the right).