Dark Matter in Axion Landscape

Abstract

If there are a plethora of axions in nature, they may have a complicated potential and create an axion landscape. We study a possibility that one of the axions is so light that it is cosmologically stable, explaining the observed dark matter density. In particular we focus on a case in which two (or more) shift-symmetry breaking terms conspire to make the axion sufficiently light at the potential minimum. In this case the axion has a flat-bottomed potential. In contrast to the case in which a single cosine term dominates the potential, the axion abundance as well as its isocurvature perturbations are significantly suppressed. This allows an axion with a rather large mass to serve as dark matter without fine-tuning of the initial misalignment, and further makes higher-scale inflation to be consistent with the scenario.

23 pages, 4 figures; references added

References in corpus (21)

• A General Analytic Formula for the Spectral Index of the Density Perturbations produced during Inflation
• Monodromy in the CMB: Gravity Waves and String Inflation
• A new approach to the evolution of cosmological perturbations on large scales
• Gravity Waves and Linear Inflation from Axion Monodromy
• A general proof of the conservation of the curvature perturbation
• Exploring the String Axiverse with Precision Black Hole Physics
• Axions : Theory and Cosmological Role
• Axion Cosmology Revisited
• Natural inflation with multiple sub-Planckian axions
• Tension between the power spectrum of density perturbations measured on large and small scales
• Multi-Natural Inflation
• Non-Gaussianity from Curvatons Revisited
• Multi-Natural Inflation in Supergravity and BICEP2
• Leptogenesis via Axion Oscillations after Inflation
• Quality of the Peccei-Quinn symmetry in the Aligned QCD Axion and Cosmological Implications
• Ultra-light Axions: Degeneracies with Massive Neutrinos and Forecasts for Future Cosmological Observations
• Axion Landscape and Natural Inflation
• Running Spectral Index from Large-field Inflation with Modulations Revisited
• Domain Wall Formation from Level Crossing in the Axiverse
• Saving Natural Inflation
• Axion domain wall baryogenesis

Cited by in corpus (12)

• The ALP miracle: unified inflaton and dark matter
• The Spectrum of the Axion Dark Sector
• Relaxing the Cosmological Moduli Problem by Low-scale Inflation
• Cosmological implications of $n_s\approx 1$ in light of the Hubble tension
• Adiabatic suppression of the axion abundance and isocurvature due to coupling to hidden monopoles
• Stochastic Axion Dark Matter in Axion Landscape
• Cosmic Axion Force
• Constraints on decaying dark matter from weak lensing and cluster counts
• Soliton Merger Rates and Enhanced Axion Dark Matter Decay
• Inflation from periodic extra dimensions
• The QCD Axion: A Unique Player in the Axiverse with Mixings
• Hidden Dark Matter from Starobinsky Inflation