Asymptotic Safety and Cosmology

The asymptotic safety approach to quantum gravity provides a possible solution to the problem of the quantization of the gravitational field. It is based on the existence of an ultraviolet non-Gaussian fixed point for the couplings of the \(\sqrt {g}R\) and \(\sqrt {g}\) operators of the Euclidean theory. The most compelling implication of this fact is a vanishing Newton’s constant G at infinitely high energies. In this review the possible strategies to implement the details of this mechanism in cosmology are presented and the results are briefly discussed. In its simplest realization the universe emerges from a state of zero entropy end evolves towards an accelerated phase driven by a time-dependent Newton constant and cosmological constant Λ according to the renormalization group for quantum gravity. In this framework bouncing and non-singular universe models can be dynamically generated from the vanishing of the Newton’s constant at high energies. Important modifications of the original R + R2 Starobinsky model are expected at the inflationary scale. Direct computations of the graviton spectral function can in principle provide the initial spectrum of gravitational waves in the early universe. At late times strong renormalization effects are expected at large cosmological scales that can drive the observed accelerated expansion of the universe. The new era of precision cosmology represents an important occasion to finally test the physical predictions of this new theory of quantum gravity.