Doctor suggests a new diet for Non-local gravity

Abstract

Many non-local modifications of the Einstein Hilbert action (involving the inverse of some differential operator acting on the Ricci scalar) have been proposed over the past 2.5 decades. They are appealing because they could effectively describe the impact of the vacuum quantum fluctuations in a curved space-time on cosmological scales, and act as a source of Dark Energy. In the first part of this seminar we will discuss the common features of these models and their compatibility with observations. In the second part we'll introduce a novel type of non-local term, inspired by Sakharov induced gravity model, and show that a completely different phenomenology could arise. Interestingly, the latter seems particularly suited to address at the same time both the $H_0$ and $\sigma_8$ cosmic tensions.