Dynamical System Analysis of Cosmologies with Running Cosmological Constant from Quantum Einstein Gravity

TL;DR

This paper explores how quantum fluctuations can cause the cosmological constant to vary over time, leading to different dark energy phases in the universe's evolution, using a dynamical systems approach.

Contribution

It introduces a nonperturbative scaling mechanism for a time-dependent vacuum energy in cosmology based on Quantum Einstein Gravity, analyzed through dynamical systems.

Findings

Identification of two dark energy regimes in cosmological evolution.

Demonstration of a transition from power-law to accelerated expansion.

Insight into quantum fluctuation effects on cosmological constant dynamics.

Abstract

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 employ the dynamical systems approach to study the qualitative behavior of 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 a "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.