Weak Gravity Conjecture for the Effective Field Theories with N Species

TL;DR

This paper proposes a new UV cutoff limit for effective field theories with many species coupled to gravity, impacting models like N-flation and multi-species gauge theories, and suggesting some may be in the swampland.

Contribution

It introduces a conjecture for the intrinsic UV cutoff in theories with multiple species, linking it to the number of fields and their interactions, which constrains the validity of certain inflationary models.

Findings

UV cutoff for scalar fields: $oxed{rac{ ext{sqrt}( ext{lambda})}{ ext{N}} M_p$}

UV cutoff for gauge theories: $oxed{rac{g M_p}{ ext{sqrt}( ext{N})}$}

Implication that some multi-field inflation models may be in the swampland.

Abstract

We conjecture an intrinsic UV cutoff for the validity of the effective field theory with a large number of species coupled to gravity. In four dimensions such a UV cutoff takes the form $\Lambda=\sqrt{\lambda/ N}M_p$ for $N$ scalar fields with the same potential $\lambda \phi_i^4$, $i=1,...,N$. This conjecture implies that the assisted chaotic inflation or N-flation might be in the swampland, not in the landscape. Similarly a UV cutoff $\Lambda=gM_p/\sqrt{N}$ is conjectured for the U(1) gauge theory with $N$ species.