Within the context of modified gravity and dark energy scenarios of the
accelerating universe, we study the stability of de Sitter space with respect
to inhomogeneous perturbations using a gauge-independent formalism. In modified
gravity the stability condition is exactly the same that one obtains from a
homogeneous perturbation analysis, while the stability condition in
scalar-tensor gravity is more restrictive.Comment: 5 pages, no figures, RevTeX, to appear in Phys. Rev. D (Rapid
  Communications section

V. Faraoni