Reheating constraints on tachyon inflation

Abstract

Tachyon inflation is one of the most attractive models of noncanonical inflation motivated by string theory. In this work we revisit the constraints on tachyon inflation with inverse cosh potential and exponential potential considering reheating, Although the phase of reheating is not well understood, it can be parametrized in terms of reheating temperature ${T}_{\mathrm{re}}$, number of e-folds during reheating ${N}_{\mathrm{re}}$ and effective equation of state during reheating ${w}_{\mathrm{re}}$, which can be related to the parameters of the tachyon potential, spectral index ${n}_{s}$ and tensor-to-scalar ratio $r$. For various reheating scenarios there is a finite range of ${w}_{\mathrm{re}}$ and the reheating temperature should be above electroweak scale. By imposing these conditions, we find that both the inverse cosh potential and exponential potential are disfavored by Planck observations. We also find that ${w}_{\mathrm{re}}$ for both these potentials should be close to 1 to satisfy Planck-2018 joint constraints on ${n}_{s}$ and $r$.