Evolution of the curvature perturbation during and after multi-field inflation

Understand

We study the evolution of the curvature perturbation on the super-horizon scales starting from the inflationary epoch until there remains only a single dynamical degree of freedom, presureless matter, in the universe.

• We consider the cosmic inflation driven by a multiple number of the inflaton fields, which decay into both radiation and pressureless matter components.
• We present a complete set of the exact background and perturbation equations which describe the evolution of the universe throughout its history.
• By applying these equations to the simple but reasonable model of multi-field chaotic inflation, we explicitly show that the total curvature perturbation is continuously varying because of the non-adiabatic components of the curvature perturbation generated by the multiple inflaton fields throughout the whole evolution of the universe.