  String/M theory inspires an uncertainty relation between space and time which
deviates from general relativity. It is possible to explore this deviation from
cosmological observations, in particular from the CMB fluctuation spectrum.
This paper extends some previous observations to more general inflation
schemes, we find that the noncommutative spacetime effects always suppress the
power spectrum, of both the scalar and tensor perturbations, and may provide a
large enough running of the spectral index to fit the WMAP data in the
inflation model.
