Quantum corrections and the Swampland

• Autores: Max Wiesner
• Directores de la Tesis: Fernando G. Marchesano Buznego (dir. tes.), Oscar Varela Rizo (tut. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2021
• Idioma: español
• Títulos paralelos:
  • Correcciones Cuánticas y el Swampland
• Tribunal Calificador de la Tesis: Timo Weigand (presid.), Angel Uranga Urteaga (secret.), Eran Palti (voc.)
• Programa de doctorado: Programa de Doctorado en Física Teórica por la Universidad Autónoma de Madrid
• Materias:
  • Física
    • Física teórica
      • Teoría cuántica de campos
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • In this thesis, we study string theory compactifications to four dimensions in the context of the Swampland Program. Our particular focus lies on the role of quantum corrections for the realisation of certain swampland conjectures in models arising from string theory.

    After reviewing some background material on string and F-theory compactifications, we start by extending the study of the Swampland Distance Conjecture to the hypermultiplet sector of type IIB string theory compactified on Calabi–Yau three-folds. Unlike its vector multiplet counterpart, the hypermultiplet moduli space is heavily affected by D- brane instantons that yield significant corrections to the effective four-dimensional theory. We investigate the effect of these D-brane instantons in regions of moduli space that are classically at infinite distance. For these we show that certain classical infinite distance singularities are generically obstructed by such quantum effects, which deflect trajectories approaching the classical infinite distance point towards a weak-coupling point. We further relate the presence of D-brane instanton corrections to the emergence of tensionless strings. In that context, we show that, via duality, those infinite distance limits persisting at the quantum level can be identified with weak-coupling limits for fundamental type II strings in accordance with the Emergent String Conjecture.

    We then move on to consider asymptotic regions in the moduli space of F-theory compactifications on elliptically fibered Calabi–Yau four-folds. In the Kähler moduli space we show that limits qualifying as emergent string limits can only be obtained if the base of the elliptically fibered Calabi–Yau four-fold is itself fibered by either a unique rational or a unique genus-one curve. In the limit of vanishing fibral volume this gives rise to a unique emergent heterotic or type II string, respectively. Importantly, an analysis of perturbative alpha'-corrections to the F-theory moduli space geometry reveals that these precisely censor classically pathological limits for which the tension of a weakly-coupled heterotic string would be parametrically below the Kaluza–Klein scale. We further investigate the effect of the perturbative alpha'-corrections to the F-theory Kähler sector on the Weak Gravity Conjecture, which on the classical level is generically satisfied by the tower of excitations of the emergent heterotic string. We argue that away from the strict weak coupling limit the super-extremality bound of the Weak Gravity Conjecture is corrected by gauge threshold and mass renormalisation effects. Duality between heterotic string theory and F-theory can then be used to match the alpha'-corrections on the F-theory side to string loop corrections on the heterotic side. Based on this and by imposing the Weak Gravity Conjecture to hold also on the quantum level, we predict the form of the mass renormalisation of the tower of string excitations.

    Finally, we investigate the complex structure moduli space of such F-theory com- pactifications in the presence of G4-flux. For an arbitrary dimension of this moduli space, we present a systematic study of the flux potential and its vacua in the large complex structure phase where each complex structure fields splits into a saxionic and an axionic component. In particular we include polynomial corrections to the leading expressions of Kähler and superpotential which, via four-fold mirror symmetry, can be identified with curvature corrections in type IIA. For one family of flux choices, these corrections ensure the stabilisation of all complex structure moduli without a parametric violation of the tadpole cancellation at the cost of setting a bound on the possible saxionic vevs. In con- trast, for a second family of flux choices, the saxionic vevs can be unbounded with the contribution to the D3-brane tadpole being independent of the dimension of the moduli space.