Isocurvature Perturbations and Reheating in Multi-Field Inflation

Understand

Inflationary models involving more than one scalar field naturally produce isocurvature perturbations.

• However, while these are fairly well studied, less is known about their evolution through the reheating epoch, when the inflationary fields decay into the standard constituents of the present universe.
• In this paper, by modelling reheating perturbatively, we calculate the power spectrum of the non-adiabatic pressure perturbation in three different inflationary models.
• We show that the isocurvature can grow large initially, but decays faster than the pressure perturbations.