Speaker
Description
Determining the active screening mechanism from a general scalar-tensor Lagrangian remains a significant challenge when testing modified gravity models against cosmological observations. In this talk, I will present a new diagnostic framework based on a systematic study of nonlinear cosmological perturbations in luminal Horndeski theories. I will outline the derivation of a master equation for screening and demonstrate how it recovers established mechanisms, such as Vainshtein and Chameleon, directly from fundamental theory. Furthermore, this framework reveals a completely new regime we term "Phaedrus" screening, characterised by a screening radius that grows linearly with the mass of the source object. For each mechanism, I will present analytical and numerical solutions, clarifying the conditions under which they activate. Finally, I will introduce the new open-source software tools that enable this work.