Perturbations of Einstein-Maxwell-dilaton fields

Expressions for the complete perturbations of the solution of the Einstein-Maxwell-dilaton equations which represents the spacetime for gravitational waves, possibly coupled with electromagnetic waves and with dilaton fields, bound to collision are determined in terms of complex scalar potentials. These expressions are obtained using Wald's method of adjoint operators without imposing any gauge condition on the perturbed tetrad. The complex scalar potentials satisfy a system of five second-order linear partial differential equations. [S0556-2821(97)07022-7].