Upper bounds on maximal matter gauge charge in string compactifications

Establish rigorous upper bounds on the maximal gauge charge achievable by matter fields in consistent string compactifications, in particular within M-theory and F-theory constructions where higher representations are possible but non-generic, thereby constraining the largest representation charges beyond the typical two-index representations prevalent in D-brane models.

Background

Light matter fields in string vacua typically appear in small gauge representations, especially in D-brane models where at most two-index representations are realized. In M-theory and F-theory compactifications, higher representations can occur but are non-generic, and current records suggest unusually large charges are possible in special cases.

A general, theory-wide bound on the maximal possible matter charge would clarify the spectrum constraints imposed by quantum gravity and guide model-building, but such bounds have not been established.