Non-commutative Power-law Inflation: Mode Equation and Spectra Index
  Following an elegant approach that merge the effects of the stringy spacetime uncertainty relation into primordial perturbations suggested by Brandenberger and Ho, we show the mode equation up to the first order of non-commutative parameter.   A new approximation is provided to calculate the mode functions analytically in the non-commutative power-law inflation models.   It turns out that non-commutativity of spacetime can provide small corrections to the power spectrum of primordial fluctuations as the first-year results of WMAP indicate. Moreover, using the WMAP data, we obtain the value of expansion parameter, non-commutative parameter and find the approximation is viable. In addition, we determined the string scale $l_s \simeq 2.0\times 10^{-29}{cm}$. 
Dao-jun Liu, Xin-zhou Li