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A linear cosmological perturbation theory of an almost homogeneous and isotropic
perfect fluid Universe with dynamically evolving Newton constant and
cosmological constant is presented. A gauge invariant formalism is
developed by means of the covariant approach, and the acoustic propagation
equations governing the evolution of the comoving fractional spatial gradients
of the matter density, , and are thus obtained. Explicit solutions
are discussed in cosmologies where both and vary according to
renormalization group equations in the vicinity of a fixed point ().

Innocenza Busa'
2005-11-14