2015/12/31 by Luis E. Ibáñez, Luis E. Ibanez, Miguel Montero +3 · 4 citations
Mathematics · Physics and Astronomy · #Axion #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Dark matter #Discrete symmetry #Dissipative system #Geometry #Gravitation #Higgs boson #Higgs field #Homogeneous space #Mathematics #Monodromy #Particle physics #Particle physics theoretical and experimental studies #Physics #Pure mathematics #Quantum mechanics #String (physics) #Strong CP problem #Symmetry (geometry) #Theoretical physics #hep-ph #hep-th
paper · pdf · doi:10.1007/jhep04(2016)020
published as J. High Energ. Phys. (2016) 2016: 20 · 26 pages + appendices, 3 figures; v3: Corrected bounds on relaxion parameter space
openalex publication_date 2016/04/01 · arxiv created 2016/07/25 · arxiv updated 2016/07/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The 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 C μνρ coupling to the SM Higgs through its field strength F 4. 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 ≃ F 4 /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.