Power-law inflation as an attractor solution for inhomogeneous cosmological models

Power-law inflation is shown to be a local attractor for t to infinity in the space of inhomogeneous solutions of the Einstein theory of gravity with a minimally coupled scalar field having a positive exponential potential. Applying the conformal equivalence theorem the authors show that a similar result holds true for fourth-order gravity with the Lagrangian L=RM, M not=, 1, 2.