M. Bertolini, P. R. Merks and D. R. Morrison, *On the global symmetries of 6D superconformal field theories*
(2015) [1510.08056] .
**Abstract:**

*We study global symmetry groups of six-dimensional superconformal field theories (SCFTs).
In the Coulomb branch we use field theoretical arguments to predict an
upper bound for the global symmetry of the SCFT.
We then analyze global symmetry groups of F-theory constructions of SCFTs with a one-dimensional Coulomb branch.
While in the vast majority of cases, all of the global symmetries allowed
by our Coulomb branch analysis can be realized in F-theory, in a handful
of cases we find that F-theory models fail to realize the full symmetry
of the theory on the Coulomb branch. In one particularly mysterious
case, F-theory models realize several distinct maximal subgroups of the
predicted group, but not the predicted group itself.*