Rescuing Massive Photons from the Swampland

TL;DR

This paper demonstrates how effective theories with massive abelian vectors that seemingly violate Swampland conjectures can be UV-completed to satisfy them, revealing new possibilities for phenomenology and dark matter models.

Contribution

The authors provide explicit UV-completions of theories with massive vectors that violate Swampland conjectures, using St"uckelberg and Higgs mechanisms with all parameters of order one.

Findings

UV-completions satisfy Swampland conjectures

Light vectors can be parametrically separated from other states

Constraints on dark photon models can be circumvented

Abstract

Stringent Swampland conjectures aimed at effective theories containing massive abelian vectors have recently been proposed (arXiv:1808.09966), with striking phenomenological implications. In this article, we show how effective theories that parametrically violate the proposed conjectures can be UV-completed into theories that satisfy them. The UV-completion is accessible through both the St\"uckelberg and Higgs mechanisms, with all dimensionless parameters taking $\mathcal{O}(1)$ values from the UV perspective. These constructions feature an IR limit containing a light vector that is parametrically separated from any other massive states, and from any cut-off scale mandated by quantum gravity consistency requirements. Moreover, the cut-off--to--vector--mass ratio remains parametrically large even in the decoupling limit in which all other massive states (including any scalar excitations) become arbitrarily heavy. We discuss how apparently strong constraints imposed by the proposed conjectures on phenomenologically interesting models, including specific production mechanisms of dark photon dark matter, are thereby circumvented.