Opening the reheating box in multifield inflation

The robustness of multi-field inflation to the physics of reheating is investigated. In order to carry out this study, reheating is described in detail by means of a formalism which tracks the evolution of scalar fields and perfect fluids in interaction (the inflatons and their decay products). This framework is then used to establish the general equations of motion of the background and perturbative quantities controlling the evolution of the system during reheating. Next, these equations are solved exactly by means of a new numerical code. Moreover, new analytical techniques, allowing us to interpret and approximate these solutions, are developed. As an illustration of a physical prediction that could be affected by the micro-physics of reheating, the amplitude of non-adiabatic perturbations in double inflation is considered. It is found that ignoring the fine-structure of reheating, as usually done in the standard approach, can lead to differences as big as similar to 50%, while our semi analytic estimates can reduce this error to similar to 10%. We conclude that, in multi-field inflation, tracking the perturbations through the details of the reheating process is important and, to achieve good precision, requires the use of numerical calculations. Superscript/Subscript Available

Automated summary

The robustness of multi-field inflation to the physics of reheating is investigated, establishing equations of motion for background and perturbative quantities and emphasizing the importance of tracking perturbations through numerical calculations for precision. Illustrating a physical prediction affected by micro-physics of reheating, the study finds significant differences when ignoring fine-structure of reheating, highlighting the necessity of considering detailed reheating processes in multi-field inflation.