A Stepping Stone Solution to the QCD Axion Isocurvature Problem

arXiv:2609.28840 · hep-ph, astro-ph.CO · Submitted 2026-09-23 · Read on arXiv

hep-ph, astro-ph.CO

Submitted: 2026-09-23

Updated: 2026-09-23

Terminology

• Benchmark — 34× in this paper · explained in 2 episodes
• Abundance — 7× in this paper · explained in 1 episode
• Domain Walls — 5× in this paper · explained in 2 episodes
• Reheating — 4× in this paper · explained in 2 episodes
• Topological Defects — 3× in this paper · explained in 2 episodes
• Fine-Tuning — 2× in this paper · explained in 5 episodes
• Nonminimal coupling — 2× in this paper · explained in 2 episodes
• Peccei Quinn — 2× in this paper
• Phase Transitions — 2× in this paper · explained in 2 episodes
• Adam — 1× in this paper · explained in 2 episodes
• Aperture — 1× in this paper · explained in 1 episode
• Symmetry Breaking — 1× in this paper · explained in 3 episodes
• pulsar timing arrays — 1× in this paper · explained in 2 episodes

Sources

• Axion Cosmology
• Probing a QCD String Axion with Precision Cosmological Measurements
• The landscape of QCD axion models
• Long-term dynamics of cosmological axion strings
• Axion isocurvature and the model-building problem of low-scale inflation
• CMB Constraints on Pre-Inflationary Axion Dark Matter Isocurvature
• BICEP / Keck XIII: Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season
• Probing Primordial Gravitational Waves: Ali CMB Polarization Telescope
• Performance forecasts for the primordial gravitational wave detection pipelines for AliCPT-1
• The Simons Observatory: Science Goals and Forecasts for the Enhanced Large Aperture Telescope
• Probing Cosmic Inflation with the LiteBIRD Cosmic Microwave Background Polarization Survey
• CMB-S4 Science Book, First Edition
• CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
• Snowmass 2021 CMB-S4 White Paper
• REMOVING THE COSMOLOGICAL BOUND ON THE AXION SCALE
• Suppressing Isocurvature Perturbations of QCD Axion Dark Matter
• Diluting the inflationary axion fluctuation by a stronger QCD in the early Universe
• Axion Misalignment Driven to the Bottom
• A Step in Flux to Suppress Axion Isocurvature
• Axion cogenesis without isocurvature perturbations

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• Axions as Dark Matter, Dark Energy, and Dark Radiation