End of multi-field inflation and the perturbation spectrum

TL;DR

This paper studies multi-field inflation models, showing that their perturbation spectra depend on mass distributions and often become redder than single-field models, with implications for cosmological observations.

Contribution

It provides a simple analysis of multi-field inflation dynamics and how mass spectra influence the perturbation spectrum, extending single-field results to multiple fields.

Findings

Perturbation spectrum depends on mass distribution and number of fields.

Massive fields cause the spectrum to become redder.

Results are similar to single-field inflation but with additional mass spectrum effects.

Abstract

We investigate the dynamics of inflation models driven by multiple, decoupled scalar fields and calculate the Hubble parameter and the amplitude of the lightest field at the end of inflation which may be responsible for interesting, or possibly dangerous cosmological consequences after inflation. The results are very simple and similar to those of the single field inflation, mainly depend on the underlying spectrum of the masses. The mass distribution is heavily constrained by the power spectrum of density perturbations P and the spectral index n. The overall mass scale gives the amplitude of P, and n is affected by the number of fields and the spacing between masses in the distribution. The drop-out effect of the massive fields makes the perturbation spectrum typically redder than the single field inflation spectrum. We illustrate this using two different mass distributions.