Metric Perturbation Approach to Gravitational Waves in Isotropic   Cosmologies
  Gravitational waves in isotropic cosmologies were recently studied using the gauge-invariant approach of Ellis-Bruni. We now construct the linearised metric perturbations of the background Robertson-Walker space-time which reproduce the results obtained in that study. The analysis carried out here also facilitates an easy comparison with Bardeen. 
E. M. O'Shea