Aspects of T-branes
Author
Schwieger, SebastiánAdvisor
Marchesano Buznego, FernandoEntity
UAM. Departamento de Física TeóricaDate
2019-03-14Subjects
Partículas (Física nuclear) - Tesis doctorales; FísicaNote
Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 14-03-2019Esta obra está bajo una licencia de Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0 Internacional.
Abstract
This thesis explores the BPS-stability of T-brane con gurations of 7-branes
including -corrections as well as stability on compact 4-cycles in the absence
of defects and including them.
First, we study '-corrections in multiple D7-brane con gurations with noncommuting
pro les for their transverse position elds. We focus on T-brane
systems, crucial in F-theory GUT model building. There 0-corrections modify
the D-term piece of the BPS equations which, already at leading order,
require a non-primitive Abelian worldvolume ux background. We nd that
0-corrections may either i) leave this ux background invariant, ii) modify the
Abelian non-primitive ux pro le, or iii) deform it to a non-Abelian pro le.
The last case typically occurs when primitive uxes, a necessary ingredient to
build 4d chiral models, are added to the system. We illustrate these three cases
by solving the 0-corrected D-term equations in explicit examples, and describe
their appearance in more general T-brane backgrounds. Finally, we discuss
implications of our ndings for F-theory GUT local models.
Secondly, we analyse global aspects of 7-brane backgrounds with a noncommuting
pro le for their worldvolume scalars, also known as T-branes. In particular,
we consider con gurations with no poles and globally well-de ned over
a compact Kähler surface. We nd that such T-branes cannot be constructed
on surfaces of positive or vanishing Ricci curvature. For the existing T-branes,
we discuss their stability as we move in Kähler moduli space at large volume
and provide examples of T-branes splitting into non-mutually-supersymmetric
constituents as they cross a stability wall.
Lastly, we consider the e ects of defects on the stability of T-brane systems.
Such defects are induced by the presence of 7-branes on additional four-cycles
intersecting the locus of the T-brane system. Coupling of the elds on both
stacks modi es the BPS-equations and we nd that it allows for T-branes on
four-cycles that do not allow for stable T-branes in absence of defects due to the
topological obstructions mentioned before. One class of these solutions feature
poles in the Higgs- eld pro le. By performing a Kaluza-Klein expansion we
show that in four dimensions the presence of these poles translates to defect zero-modes giving a vev to KK-modes. Finally, by taking a suitable limit, we
show that in the case of a self-intersecting four-cycle, the defect picture can be
linked to an eight-dimensional Higgs- eld valued in a larger gauge algebra.
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Google Scholar:Schwieger, Sebastián
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