Noncommutative Inflation and the CMB Multipoles

The first year results of WMAP tentatively indicate running of the spectral index as well as a deficit of power in the low multipoles in the CMB spectrum. The former can be rather easily understood in the noncommutative inflation model, and the latter, as we shall show in this paper, still appears to be an anomaly, even though the noncommutative inflation model already suppresses the low multipoles to a certain degree. By fitting the power spectrum, we determine the string scale to be $l_s\sim 4\times 10^{-29}$cm.