March 21, 14:15 in A315   

Ippocratis Saltas (Sussex U., Brighton, UK)


f(R) gravity from the renormalisation group

I will discuss the cosmology resulting from a Renormalisation Group (RG) improvement of the Einstein--Hilbert action, in the context of the Asymptotic Safety scenario, where both Newton's and cosmological constant run with the energy scale. In particular, I will focus on viewing the RG improved action as an effective f(R) model and then discuss its corresponding cosmological UV and IR dynamics. As I will show, the effective f(R) model has some remarkable properties: It naturally describes a non-singular Universe, giving rise to a primordial and late time acceleration period, with exponentially separated scales, on the same time exhibiting a radiation and matter domination era. I will also explain how the model behaves as R^2 gravity at very high energies, while it correctly recovers General Relativity at solar system scales. Finally, I will discuss about the primordial fluctuations, which in this simplified model turn out to be too large to be the observed ones, and more ingredients in the action are needed.