Refined Study of Isocurvature Fluctuations in the Curvaton Scenario

Understand

We revisit the generation of dark matter isocurvature perturbations in the curvaton model in greater detail, both analytically and numerically.

• As concrete examples, we investigate the cases of thermally decoupled dark matter and axionic dark matter.
• We show that the radiation produced by the decay of the curvaton, which has not been taken into account in previous analytical studies, can significantly affect the amplitude of isocurvature perturbations.
• In particular, we find that they are drastically suppressed even when the dark matter freeze-out (or the onset of the axion oscillations for axionic dark matter) occurs before the curvaton decays, provided the freeze-out takes place deep in the curvaton-dominated Universe.