Constraining Curvatonic Reheating

TL;DR

This paper provides the first observational constraints on reheating in inflation models with an extra light scalar field, showing how such fields influence reheating temperature bounds and the post-inflationary expansion history.

Contribution

It systematically constrains reheating parameters in curvaton-like models, extending previous single-field analyses to include additional scalar fields and their effects.

Findings

Lower reheating temperatures are favored with an extra scalar field.

In quartic inflation, an upper bound of 5×10^4 GeV on reheating temperature is established.

Reheating information content varies, being modest in plateau inflation but substantial in quartic inflation.

Abstract

We derive the first systematic observational constraints on reheating in models of inflation where an additional light scalar field contributes to primordial density perturbations and affects the expansion history during reheating. This encompasses the original curvaton model but also covers a larger class of scenarios. We find that, compared to the single-field case, lower values of the energy density at the end of inflation and of the reheating temperature are preferred when an additional scalar field is introduced. For instance, if inflation is driven by a quartic potential, which is one of the most favoured models when a light scalar field is added, the upper bound $T_{\mathrm{reh}}<5\times 10^{4}\,\mathrm{GeV}$ on the reheating temperature $T_{\mathrm{reh}}$ is derived, and the implications of this value on post-inflationary physics are discussed. The information gained about reheating is also quantified and it is found that it remains modest in plateau inflation (though still larger than in the single-field version of the model) but can become substantial in quartic inflation. The role played by the vev of the additional scalar field at the end of inflation is highlighted, and opens interesting possibilities for exploring stochastic inflation effects that could determine its distribution.