Dynamical system analysis of cosmologies with running cosmological constant from quantum Einstein gravity.

We discuss a mechanism that induces a time-dependent vacuum energy on cosmological scales. It is based on the instability-induced renormalization triggered by the low-energy quantum fluctuations in a Universe with a positive cosmological constant. We use the dynamical systems approach to study the qualitative behavior of the Friedmann-Robertson-Walker cosmologies where the cosmological constant is dynamically evolving according with this nonperturbative scaling at low energies. It will be shown that it is possible to realize 'two regimes' dark energy phases, where an unstable early phase of power-law evolution of the scale factor is followed by an accelerated expansion era at late times. [ABSTRACT FROM AUTHOR]