IIB string theory explored: Reflection 7-branes

The authors argue for the existence of a new object in string theory which they dub Reflection 7-Branes (R7-branes). so-called cobordism conjecture, is analogous to conjecture that quantum gravity does not allow global symmetries, implies these objects are present certain type IIB backgrounds, as demonstrate. It shown R7-branes non-supersymmetric, strings can end on them, and 3-form field lives its worldvolume.