Temporal enhancement of super-horizon curvature perturbations from decays of two curvatons and its cosmological consequences

Understand

If more than one curvaton dominate the Universe at different epochs from each other, curvature perturbations can be temporarily enhanced to a value much larger than the observed one 10^{-5}.

• The traces of the enhancement may be left as higher order correlation functions, that is, as non-Gaussianity, the stochastic gravitational waves that are sourced by scalar-scalar mode couplings, as well as the primordial black holes that are formed by the gravitational collapse of the enhanced curvature perturbations.
• We first confirm that such a temporal enhancement indeed occurs by solving the linearized perturbation equations both numerically and analytically.
• We then derive an analytic expression of the full-order curvature perturbation which does not rely on the frequently used sudden decay approximation and is exact on super-horizon scales.