Relaxion monodromy and the Weak Gravity Conjecture

By Luis E Ibáñez, M. Montero, A. Uranga, I. Valenzuela. 2015

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A bstractThe recently proposed relaxion models require extremely large trans-Planckian axion excursions as well as a potential explicitly violating the axion shift symmetry. The latter property is however inconsistent with the axion periodicity, which corresponds to a gauged discrete shift symmetry. A way to make things consistent is to use monodromy, i.e. both the axion and the potential parameters transform under the discrete shift symmetry. The structure is better described in terms of a 3-form field Cμνρ coupling to the SM Higgs through its field strength F4. The 4-form also couples linearly to the relaxion, in the Kaloper-Sorbo fashion. The extremely small relaxion-Higgs coupling arises in a see-saw fashion as g ≃ F4/f , with f being the axion decay constant. We discuss constraints on this type of constructions from membrane nucleation and the Weak Gravity Conjecture. The latter requires the existence of membranes, whose too fast nucleation could in principle drive the theory out of control, unless the cut-off scale is lowered. This allows to rule out the simplest models with the QCD axion as relaxion candidate on purely theoretical grounds. We also discuss possible avenues to embed this structure into string theory.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/f4c85bdc417f79c673dcb8d06996ae313359c687

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Citations in the corpus

A Tower Weak Gravity Conjecture from Infrared Consistency (2018, background): “1)-form elds. In particular, the 0-form (axion) version of the conjecture has generated a lot of activity in recent years since it may imply strong constraints on large-eld in ation [2{19] (see also [13,20,21] for an application to cosmological relaxation). Moreover, it has recently been realized th”
Evidence for a sublattice weak gravity conjecture (2016, background): “From a phenomenological perspective, the WGC is especially interesting due to its ability to constrain models of large-field axion inflation [6–25].”
The Weak Gravity Conjecture in three dimensions (2016, methodology): “In particular, it has been recently applied to large-field inflationary models and relaxions [2–22].”
The Swampland: Introduction and Review (2019, methodology): “potentials and three-forms as been developed in [353{356] and utilised in the context of in ation in [337,357]. This relation has been extensively studied in string theory in a recent program of work [132,138,160,315,330,358{372]. Let us introduce the idea through a simple toy model, following the n”