Perturbed Power-law parameters from WMAP7
  We present a perturbative approach for studying inflation models with soft
departures from scale free spectra of the power law model. In the perturbed
power law (PPL) approach one obtains at the leading order both the scalar and
tensor power spectra with the running of their spectral indices, in contrast to
the widely used slow roll expansion. The PPL spectrum is confronted data and we
show that the PPL parameters are well estimated from WMAP-7 data.
