title: Axions, Wormholes and Inflation in the String Landscape
creator: Mangat, Patrick
subject: 530
subject: 530 Physics
description: This thesis explores the string theory landscape in two distinct approaches. First, we study dark radiation predictions in Large Volume Scenarios (LVS). Specifically, we realise the visible sector by D7-branes wrapping a 4-cycle. In consequence, the tension between the predicted effective number of relativistic species and recent cosmological measurements is reduced, and further ameliorated by accepting fine-tuning. Next, we investigate whether large-field inflation is consistent with quantum gravity. We propose realisations of axion monodromy inflation and alignment inflation in string theory. Due to backreaction of moduli on the inflaton, axion monodromy inflation requires potentially severe fine-tuning, which we realise on Calabi-Yau 4-folds, whereas we find no-go results on Calabi-Yau 3-folds. The severity of the tunings is quantified by the diminution of the landscape vacua after imposing the fine-tuning conditions. Furthermore, alignment inflation is realised by a winding trajectory in the field space of two complex structure moduli. Severe fine-tuning seems avoidable and consistency with the mild Weak Gravity Conjecture possible, albeit not with its strong version. Finally, we investigate the role of gravitational instantons for axion inflation. Although Giddings-Strominger wormholes are shown to induce corrections to the axion potential, a derivation of  relevant constraints on the axion field range remains challenging.
date: 2017
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/22967/1/Thesis_PMangat.pdf
identifier: DOI:10.11588/heidok.00022967
identifier: urn:nbn:de:bsz:16-heidok-229671
identifier:   Mangat, Patrick  (2017) Axions, Wormholes and Inflation in the String Landscape.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/22967/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng