Abstract:
Five-dimensional superconformal field theories are often intrinsically strongly coupled and lack a conventional Lagrangian description. String theory nevertheless provides concrete constructions of these theories through M-theory on singular Calabi–Yau threefolds and Type IIB (p,q)-five-brane webs.
The first part of this talk will be an introduction to five-brane webs and generalised global symmetries. I will then explain how one-form symmetries can be determined directly from the brane picture. Line operators are represented by D3-branes and attached strings, while screening by local operators is realised through string junctions, Higgsing and Hanany–Witten transitions. For ordinary brane webs, this microscopic picture reproduces the results previously obtained in the literature.
I will finally discuss how the analysis is extended in the presence of orientifold O7 and O5 planes. In webs containing O5-planes, Wilson lines in spinor representations are described using half-D3-branes confined to the orientifold. A key outcome is that the one-form symmetry cannot always be inferred from the asymptotic brane charges alone: it can depend on the local structure of the web near the O5-plane.