Reheating constraints on a two-field inflationary model

Abstract

Once inflation comes to an end, the Universe enters a short stage named reheating. Making coherent oscillations about the minimum of its potential, the inflaton field transforms into the particles that occupy the Universe at later times. Yet, there is no direct cosmological observables corresponding to the reheating epoch. However, one can achieve some indirect limits, simply by taking into account cosmological evolution for observable CMB scales between the Hubble crossing time during inflation and the present time, for example. Moreover, since the reheating period takes place before the radiation dominated era, it can be modeled by an effective equation-of-state parameter, wreh. There is a limited range of reasonable values for wreh which can be regarded as the reheating period. In this paper, considering a two-field model, we investigate the reheating epoch so as to impose some constraints on the parameter space of the model. To do so, we are first required to obtain the reheating e-folds number as well as its temperature. These parameters can be written in terms of the scalar spectral index which let us perform numerical analysis in this model. Therefore, we can set some constraints on the reheating parameters which correspond to observationally viable values of the scalar spectral index.