A Bump in the Blue Axion Isocurvature Spectrum

Understand

Blue axion isocurvature perturbations are both theoretically well-motivated and interesting from a detectability perspective.

• These power spectra generically have a break from the blue region to a flat region.
• Previous investigations of the power spectra were analytic, which left a gap in the predicted spectrum in the break region due to the non-applicability of the used analytic techniques.
• We therefore compute the isocurvature spectrum numerically for an explicit supersymmetric axion model.