We present constraints on the reheating era within the string fiber inflation scenario, in terms of the effective equation-of-state parameter of the reheating fluid, $w_{\mathrm{reh}}$. The results of the analysis, completely independent on the details of the inflaton physics around the vacuum, illustrate the behavior of the number of $e$-foldings during the reheating stage, $N_{\mathrm{reh}}$, and of the final reheating temperature, $T_{\mathrm{reh}}$, as functions of the scalar spectral index, $n_s$. We analyze our results with respect to the current bounds given by the Planck mission data and to upcoming cosmological experiments. We find that large values of the equation-of-state parameter ($w_{\mathrm{reh}}>1/3$) are particularly favored as the scalar spectral index is of the order of $n_s\sim 0.9680$, with a ${\sigma }_{n_s}\sim 0.002$ error. Moreover, we compare the behavior of the general reheating functions $N_{\mathrm{reh}}$ and $T_{\mathrm{reh}}$ in the fiber inflation scenario with the one extracted by the class of the $\alpha$-attractor models with $\alpha =2$. We find that the corresponding reheating curves are very similar in the two cases.

• Received 7 April 2017

DOI:https://doi.org/10.1103/PhysRevD.95.123528