A note on the WGC, effective field theory and clockwork within string theory
The Journal of High Energy Physics, 2018, 2018(2): 057.
It has been recently argued that Higgsing of theories with U(1)(n) gauge interactions consistent with the Weak Gravity Conjecture (WGC) may lead to effective field theories parametrically violating WGC constraints. The minimal examples typically involve Higgs scalars with a large charge with respect to a U(1) (e.g. charges (Z, 1) in U(1)(2) with Z >> 1). This type of Higgs multiplets play also a key role in clockwork U(1) theories. We study these issues in the context of heterotic string theory and find that, even if there is no new physics at the standard magnetic WGC scale Lambda similar to M-gIR(P), the string scale is just slightly above, at a scale similar to root k(IR)Lambda. Here k(IR) is the level of the IR U(1) worldsheet current. We show that, unlike the standard magnetic cutoff, this bound is insensitive to subsequent Higgsing. One may argue that this constraint gives rise to no bound at the effective field theory level since k(IR) is model dependent and in general unknown. However there is an additional constraint to be taken into account, which is that the Higgsing scalars with large charge Z should be part of the string massless spectrum, which becomes an upper bound k(IR)
Effective Field Theories; Superstrings and Heterotic Strings; Spontaneous Symmetry Breaking