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School of Physics and Astronomy

Cosmology seminar - Shubham Maheshwari (University of Groningen)

23 September 2020

Time: 3:30 - 4:30pm
Speaker: Shubham Maheshwari (University of Groningen)

Stable, ghost-free solutions in UV non-local gravity

I consider higher derivative, UV modifications to GR. In particular, I will focus on a specific kind of string theory-inspired higher derivative gravity where one includes derivatives to all orders in the action. First, I will discuss how such a non-local theory of gravity admits stable, non-singular bouncing solutions in the absence of matter. Moreover, around this bouncing background, there exists only one propagating (and ghost-free) scalar mode, and no vector or tensor modes. Next, I will discuss the general analysis of scalar-vector-tensor perturbations in non-local gravity - in particular, I will show how non-local gravity is ghost-free around (A)dS and certain non-maximally symmetric backgrounds, and how certain (A)dS backgrounds have special physical spectra in that the propagating degrees of freedom are different from usual expectations.