Note on Power-Law Inflation in Noncommutative Space-Time

In this paper, we propose a new method to calculate the mode functions in the noncommutative power-law inflation model. In this model, all the modes created when the stringy space-time uncertainty relation is satisfied are generated inside the Hubble horizon during inflation. It turns out that a linear term describing the noncommutative space-time effect contributes to the power spectra of the scalar and tensor perturbations. Confronting this model with latest results from \textit{Planck} and BICEP2, we constrain the parameters in this model and we find it is well consistent with observations.