Cosmologically allowed regions for the axion decay constant $F_a$

Abstract

If the Peccei-Quinn symmetry is already broken during inflation, the decay constant $F_a$ of the axion can be in a wide region from $10^{11}$ GeV to $10^{18}$ GeV for the axion being the dominant dark matter. In this case, however, the axion causes the serious cosmological problem, isocurvature perturbation problem, which severely constrains the Hubble parameter during inflation. The constraint is relaxed when Peccei-Quinn scalar field takes a large value $\sim M_p$ (Planck scale) during inflation. In this letter, we point out that the allowed region of the decay constant $F_a$ is reduced to a rather narrow region for a given tensor-to-scalar ratio $r$ when Peccei-Quinn scalar field takes $\sim M_p$ during inflation. For example, if the ratio $r$ is determined as $r\gtrsim 10^{-3}$ in future measurements, we can predict $F_a\simeq (0.1-1.4)\times 10^{12}$ GeV for domain wall number $N_{\text{DW}}=6$.

9 pages, 1 figure, LaTeX; some explanations and references added

References in corpus (3)

• String theoretic QCD axions in the light of PLANCK and BICEP2
• Axion Dark Matter with High-Scale Inflation
• Domain wall and isocurvature perturbation problems in a supersymmetric axion model

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• Axion Model with Intermediate Scale Fermionic Dark Matter
• SMART U(1)${}_X$ $-$ Standard Model with Axion, Right handed neutrinos, Two Higgs doublets and U(1)${}_X$ gauge symmetry
• Proton Decay and Axion Dark Matter in SO(10) Grand Unification via Minimal Left-Right Symmetry
• A Dynamical Solution to the Axion Domain Wall Problem
• Axion and FIMP Dark Matter in a $U(1)$ extension of the Standard Model
• High Reheating Temperature without Axion Domain Walls
• Repercussions of the Peccei-Quinn axion on QCD
• The Search for the Cosmological Axion -- A New Refined Narrow Mass Window and Detection Scheme
• Effective ALP-Photon Coupling in External Magnetic Fields