Non-abelian R-symmetry defects from probe brane configuration in holography

In quantum field theory, symmetries are traditionally associated with conserved currents and charges. A more modern and more general characterization—valid also for discrete and higher-form symmetries—identifies symmetry generators with topological defects: extended operators whose correlation functions are invariant under smooth deformations of their worldvolumes. In this framework, conservation laws are encoded in the topological nature of these defects rather than in local currents. The aim of this thesis is to investigate how such symmetry defects, and in particular those associated with non-abelian R-symmetries, are realized in the context of holography. Understanding their holographic realization is especially important for clarifying the ultraviolet fate of symmetry defects in a theory of quantum gravity, where purely field-theoretic notions of topological operators may receive nontrivial gravitational corrections. In this respect, top-down holographic models provide a controlled and predictive playground in which these questions can be addressed. Recent proposals suggest that these defects admit a gravitational description in terms of specific probe brane configurations that are anchored at the AdS boundary but extend a finite distance into the bulk. These objects can be viewed as a regularized version of a brane–antibrane system and are conjectured to generate the full non-abelian R-symmetry group through their topological properties. In this work we test this proposal in an explicit top-down holographic background that has not previously been explored from this perspective, namely type IIA string theory on AdS_7×M_3. This geometry is dual to families six-dimensional superconformal field theories with non-abelian R-symmetry. By constructing and analyzing the corresponding probe brane defects, we provide new evidence for their role as holographic realizations of non-abelian symmetry generators and clarify how R-symmetry is encoded in the bulk through topological brane configurations.