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Effective field theories of gravity: a top-down approach

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Title: Effective field theories of gravity: a top-down approach
Authors: Harrold, Alexander
Item Type: Thesis or dissertation
Abstract: From water boiling to the behaviour of magnets, the world around us is often described using the language of Effective Field Theory. This powerful framework is often employed to model a system in terms of its low energy degrees of freedom without much thought being given to the higher energy origins of the model. In this thesis we shall attempt to turn this idea on its head by constructing effective theories by beginning from the high energy theory and then arriving at the low energy description. Our main aim shall be to address this issue in the context of deriving the EFT of perturbations around a background solution of Type IIA Supergravity given by Crampton, Pope and Stelle that involves the non-compact hyperbolic space H 2,2 . Studying the subject of EFTs in the context of Type IIA Supergravity presents it’s own challenges as this theory exists in ten spacetime dimensions, whilst our observed universe is four dimensional. We shall present how to address this issue of dimensional mismatch using Kaluza-Klein methods and discuss aspects of the resulting lower dimensional field with an eye towards achieving lower dimensional diffeomorphism invariance. This treatment shall lead us to the conclusion that a previously undiscovered Stueckelberg field must be accounted for and dealt with if one is to appropriately understand the lower dimensional theory. We also exhibit a generalisation of the solutions of Crampton, Pope and Stelle to include time dependence. Such solutions may have applications to cosmological models.
Content Version: Open Access
Issue Date: Sep-2019
Date Awarded: Apr-2020
URI: http://hdl.handle.net/10044/1/83508
DOI: https://doi.org/10.25560/83508
Copyright Statement: Creative Commons Attribution NonCommercial Licence
Supervisor: Stelle, Kellogg
Department: Physics
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Physics PhD theses

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