An Axion-induced SM/MSSM Higgs Landscape and the Weak Gravity Conjecture

TL;DR

This paper constructs models where the Higgs mass scans across a landscape via axion fields and 3-forms, exploring implications for the weak gravity conjecture and supersymmetry fine-tuning.

Contribution

It introduces novel landscape models coupling the SM and MSSM to monodromy axions and 3-forms, linking Higgs mass scanning to the weak gravity conjecture.

Findings

Higgs mass can scan in a landscape with steps determined by axion parameters.

The weak gravity conjecture constrains membrane tensions and introduces new physics thresholds.

Landscape models provide a potential explanation for MSSM fine-tuning.

Abstract

We construct models in which the SM Higgs mass scans in a landscape. This is achieved by coupling the SM to a monodromy axion field through Minkowski 3-forms. The Higgs mass scans with steps given by delta(m_H^2)= eta mu f, where mu and f are the axion mass and periodicity respectively, and eta measures the coupling of the Higgs to the associated 3-form. The observed Higgs mass scale could then be selected on anthropic grounds. The monodromy axion may have a mass mu in a very wide range depending on the value of eta, and the axion periodity f. For eta=1 and f = 10^10 GeV, one has 10^{-3}eV < mu < 10^3 eV, but ultralight axions with e.g. mu = 10^{-17} eV are also possible. In a different realization we consider landscape models coupled to the MSSM. In the context of SUSY, 4-forms appear as being part of the auxiliary fields of SUSY multiplets. The scanning in the 4-forms thus translate into a landscape of vevs for the N=1 auxiliary fields and hence as a landscape for the soft terms. This could provide a rationale for the MSSM fine-tuning suggested by LHC data. In all these models there are 3-forms coupling to membranes which induce transitions between different vacua through bubble nucleation. The Weak Gravity Conjecture (WGC) set limits on the tension of these membranes and implies new physics thresholds well below the Planck scale. More generaly, we argue that in the case of string SUSY vacua in which the Goldstino multiplet contains a monodromy axion the WGC suggests a lower bound on the SUSY breaking scale m_{3/2} > M_s^2/M_p.