A Hint of a Blue Axion Isocurvature Spectrum?

Abstract

It is known that if the Peccei-Quinn symmetry breaking field is displaced from its minimum during inflation, the axion isocurvature spectrum is generically strongly blue tilted with a break transition to a flat spectrum. We fit this spectrum (incorporated into the "vanilla" $\Lambda$-CDM cosmological model) to the Planck and BOSS DR11 data and find a mild hint for the presence of axionic blue-tilted isocurvature perturbations. We find the best fit parameter region is consistent with all of the dark matter being composed of QCD axions in the context of inflationary cosmology with an expansion rate of order $10^8$ GeV, the axion decay constant of order $10^{13}$ GeV, and the initial misalignment angle of order unity. Intriguingly, isocurvature with a spectral break may at least partially explain the low-$\ell$ vs. high-$\ell$ anomalies seen in the CMB data.

25 pages

References in corpus (9)

• Clustering of dark matter tracers: generalizing bias for the coming era of precision LSS
• Flowing with Time: a New Approach to Nonlinear Cosmological Perturbations
• Understanding higher-order nonlocal halo bias at large scales by combining the power spectrum with the bispectrum
• Isocurvature bounds on axions revisited
• The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Signs of neutrino mass in current cosmological datasets
• Axion isocurvature fluctuations with extremely blue spectrum
• Probing a QCD String Axion with Precision Cosmological Measurements
• Elementary Theorems Regarding Blue Isocurvature Perturbations
• A Bump in the Blue Axion Isocurvature Spectrum

Cited by in corpus (8)

• Planck 2018 results. X. Constraints on inflation
• Gravitational waves from dark matter isocurvature
• Axion Isocurvature Perturbations in Low-Scale Models of Hybrid Inflation
• Searching for blue in the dark
• Spectator dark matter in non-standard cosmologies
• Probing isocurvature perturbations with 21-cm global signal in the light of HERA result
• Scalar-induced gravitational waves including isocurvature perturbations with lattice simulations
• An Analytic Treatment of Underdamped Axionic Blue Isocurvature Perturbations