Abstracto
- By using the approach to the Einstein field equations based on the existence of a congruence of null two‐dimensional surfaces, it is shown that a scalar potential that satisfies a second‐order linear partial differential equation generates gravitational perturbations of a given algebraically special solution of the Einstein vacuum field equations with cosmological constant. Generalizations of this result to the case of simultaneous perturbations of the gravitational and the matter fields are also indicated.