Bonetti, Federico (2014): Effective actions for Ftheory compactifications and tensor theories. Dissertation, LMU München: Faculty of Physics 

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Abstract
In this thesis we study the lowenergy effective dynamics emerging from a class of Ftheory compactifications in four and six dimensions. We also investigate sixdimensional supersymmetric quantum field theories with selfdual tensors, motivated by the problem of describing the longwavelength regime of a stack of M5branes in Mtheory. These setups share interesting common features. They both constitute examples of intrinsically nonperturbative physics. On the one hand, in the context of Ftheory the nonperturbative character is encoded in the geometric formulation of this class of string vacua, which allows the complexified string coupling to vary in space. On the other hand, the dynamics of a stack of multiple M5branes flows in the infrared to a novel kind of superconformal field theories in six dimensions  commonly referred to as (2,0) theories  that are expected to possess no perturbative weakly coupled regime and have resisted a complete understanding so far. In particular, no Lagrangian description is known for these models. The strategy we employ to address these two problems is also analogous. A recurring Leitmotif of our work is a transdimensional treatment of the system under examination: in order to extract information about dynamics in $d$ dimensions we consider a (d1)dimensional setup. As far as Ftheory compactifications are concerned, this is a consequence of the duality between Mtheory and Ftheory, which constitutes our main tool in the derivation of the effective action of Ftheory compactifications. We apply it to sixdimensional Ftheory vacua, obtained by taking the internal space to be an elliptically fibered CalabiYau threefold, but we also employ it to explore a novel kind of Ftheory constructions in four dimensions based on manifolds with Spin(7) holonomy. With reference to sixdimensional (2,0) theories, the transdimensional character of our approach relies in the idea of studying these theories in five dimensions. Indeed, we propose a Lagrangian that is formulated in five dimensions but has the potential to capture the sixdimensional interactions of (2,0) theories. This investigation leads us to explore in closer detail the relation between physics in five and in six dimensions. One of the outcomes of our exploration is a general result for oneloop corrections to ChernSimons couplings in five dimensions.
Item Type:  Thesis (Dissertation, LMU Munich) 

Keywords:  Ftheory, (2,0) theory, effective action, ChernSimons, selfdual tensor 
Subjects:  500 Natural sciences and mathematics 500 Natural sciences and mathematics > 530 Physics 
Faculties:  Faculty of Physics 
Language:  English 
Date of oral examination:  30. June 2014 
1. Referee:  Lüst, Dieter 
MD5 Checksum of the PDFfile:  7e90b5184e5d41e543eef15261b0a2d2 
Signature of the printed copy:  0001/UMC 22173 
ID Code:  17140 
Deposited On:  16. Jul 2014 14:15 
Last Modified:  20. Jul 2016 10:36 