Daniela Saadeh
Institute of Cosmology & Gravitation, University of Portsmouth, UK

Abstract
The phenomenology of dark energy may be explained by an extra scalar particle mediating a fifth force at cosmological scales. However, stringent limits on the existence of extra forces have been placed by solar-system experiments: viable models must therefore be able to screen (i.e. suppress) the fifth force in environments where it is known to be small.
Several screening mechanisms have been proposed. However, progress in understanding their behaviour has been hindered by the complexity of the field equations involved, which are nonlinear in nature and characterised by a large hierarchy of scales. This is especially true of Vainshtein screening, where the fifth force is suppressed by high-order derivative terms becoming dominant within a large Vainshtein radius. I will present phi-enics, a numerical code based on the finite element method that can be used to overcome this problem.
I will use phi-enics to perform a theoretical test of Vainshtein screening, by comparing the behaviour of a set of massive Galileon theories exhibiting screening with their UV completion. We show that the screening does not survive the extension, casting doubt over whether Vainshtein screening can take place within the limits of validity of the theories that invoke it.

2022 February 21, 16:30

IA
Online broadcast (Zoom)