Signatures of Extra Dimensions at e-gamma and gamma-gamma Colliders
  We study the processes \gamma \e -> \gamma \e and \gamma \gamma -> \gamma \gamma, in the context of the proposal for Weak Scale Quantum Gravity (WSQG) with large extra dimensions. With an ultraviolet cutoff $M_S \sim 1$ TeV for the effective gravity theory, the cross sections obtained for these processes at the Next Linear Collider (NLC), with the \e \gamma an \gamma \gamma options, deviate from the predictions of the Standard Model significantly. Our results suggest that, for typical proposed NLC energies and luminosities, the predictions of WSQG can be tested in the range 1 TeV \lsim M_S \lsim 10 TeV, making \e \gamma an \gamma \gamma colliders important tools for probing WSQG. 
Hooman Davoudiasl