6D SCFTs, center-flavor symmetries, and Stiefel-Whitney compactifications

The center-flavor symmetry of a gauge theory specifies the global form of consistent gauge and flavor bundle background field configurations. For 6D gauge theories which arise from a tensor branch deformation of a superconformal field theory (SCFT), we determine the global structure of such background field configurations, including possible continuous Abelian symmetry and R-symmetry bundles. Proceeding to the conformal fixed point, this provides a prescription for reading off the global form of the continuous factors of the zero-form symmetry, including possible nontrivial mixing between flavor and R-symmetry. As an application, we show that this global structure leads to a large class of 4D N = 2 SCFTs obtained by compactifying on a T-2 in the presence of a topologically nontrivial flat flavor bundle characterized by an 't Hooft magnetic flux. The resulting Stiefel-Whitney twisted compactifications realize several new infinite families of 4DN = 2 SCFTs, and also furnish a 6D origin for a number of recently discovered rank one and two 4D N = 2 SCFTs.

Automated summary

The center-flavor symmetry determines the global form of background field configurations in gauge theories. We determine the global structure of such configurations in 6D gauge theories, including possible continuous Abelian symmetry and R-symmetry. This has important implications for understanding 4D SCFTs.