Wolf, Florian (2018): Towards underlying quantum gravity constraints on string inflation. Dissertation, LMU München: Faculty of Physics 

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Abstract
Inflation is a widely accepted concept in cosmology proposing an accelerated expansion of the very early universe. For the class of largefield inflation models the energy driving the expansion arises from a scalar inflaton field that traverses transPlanckian distances in a suitable potential. This thesis aims to discuss whether there exist underlying string theory or quantum gravity principles constraining/forbidding largefield inflation. Our framework is axion inflation and its interplay with moduli stabilization in string theory. Axionic inflaton fields appear naturally in string compactifications and are protected from UV corrections due to their shift symmetry. The thesis is basically organized as follows: first, attempting to engineer a fullyfledged model of largefield inflation within string theory and second, analyzing possible underlying quantum gravity reasons to explain the ubiquitous control issues. More precisely, we investigate aligned inflation in the vicinity of a conifold in the complex structure moduli space as well as axion monodromy inflation for a D7brane position modulus. The ultimate failure of all scenarios boils down to the violation of a sophisticated mass hierarchy that is required to justify the employed effective field theories. These obstacles can be traced back to the swampland conjectures which had been claimed to hold generically for effective theories deduced from quantum gravity. In order to gather more evidence for these conjectures we investigate geodesic distances in moduli spaces of various CalabiYau manifolds. Our results strongly support one of the swampland conjectures that predicts a break down of the effective theory of inflation as soon as one moves transPlanckian distances. If true, parametrically controllable models of large single field inflation seem to be impossible in string theory.
Item Type:  Theses (Dissertation, LMU Munich) 

Subjects:  500 Natural sciences and mathematics 500 Natural sciences and mathematics > 530 Physics 
Faculties:  Faculty of Physics 
Language:  English 
Date of oral examination:  18. October 2018 
1. Referee:  Blumenhagen, Ralph 
MD5 Checksum of the PDFfile:  2b3501226b11c3fa55d717043b4e5f06 
Signature of the printed copy:  0001/UMC 25923 
ID Code:  23310 
Deposited On:  10. Dec 2018 14:44 
Last Modified:  23. Oct 2020 16:25 