Inflationary Axion Isocurvature in the CMB across All Ultralight Masses

arXiv:2608.07803 · astro-ph.CO, hep-ph · Submitted 2026-08-07 · Read on arXiv

Rayne Liu, Wayne Hu, Daniel Grin

astro-ph.CO, hep-ph

Submitted: 2026-08-07

Updated: 2026-08-11

Comments: 19 pages, 17 figures. Comments are welcome

Code: https://github.com/dgrin1/axioncamb

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Accuracy — 45× in this paper · explained in 1 episode
• Abundance — 42× in this paper · explained in 1 episode
• Anisotropy — 7× in this paper · explained in 3 episodes
• Degeneracy — 4× in this paper · explained in 3 episodes
• Weak Lensing — 4× in this paper · explained in 2 episodes
• Calibration — 3× in this paper · explained in 7 episodes
• Consistency — 2× in this paper · explained in 3 episodes
• Matter Power Spectrum — 2× in this paper · explained in 2 episodes
• Fisher Information — 1× in this paper · explained in 3 episodes
• Generalization — 1× in this paper · explained in 13 episodes
• Symmetry Breaking — 1× in this paper · explained in 3 episodes
• Trace — 1× in this paper · explained in 2 episodes

Sources

• Axions In String Theory
• Probing a QCD String Axion with Precision Cosmological Measurements
• Axion Cosmology and the Energy Scale of Inflation
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Axiverse cosmology and the energy scale of inflation
• Tensor Detection Severely Constrains Axion Dark Matter
• Axion cold dark matter in view of BICEP2 results
• Using the Full Power of the Cosmic Microwave Background to Probe Axion Dark Matter
• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• A search for ultra-light axions using precision cosmological data
• An assessment of the "too big to fail" problem for field dwarf galaxies in view of baryonic feedback effects
• Ultralight scalars as cosmological dark matter
• First constraints on fuzzy dark matter from Lyman-$\alpha$ forest data and hydrodynamical simulations
• Relaxation in a Fuzzy Dark Matter Halo
• Strong bound on canonical ultra-light axion dark matter from the Lyman-alpha forest
• Don't cross the streams: caustics from Fuzzy Dark Matter
• Fuzzy Dark Matter and the Dark Energy Survey Year 1 Data
• Constraining Ultralight Axions with Galaxy Surveys
• Ultra-light axions and the $S_8$ tension: joint constraints from the cosmic microwave background and galaxy clustering
• High-redshift, small-scale tests of ultralight axion dark matter using Hubble and Webb galaxy UV luminosities

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