The Shape of the Primordial Power Spectrum: A Last Stand Before Planck
  We present a minimally-parametric reconstruction of the primordial power
spectrum using the most recent cosmic microwave background and large scale
structure data sets. Our goal is to constrain the shape of the power spectrum
while simultaneously avoiding strong theoretical priors and over-fitting of the
data. We find no evidence for any departure from a power law spectral index. We
also find that an exact scale-invariant power spectrum is disfavored by the
data, but this conclusion is weaker than the corresponding result assuming a
theoretically-motivated power law spectral index prior. The reconstruction
shows that better data are crucial to justify the adoption of such a strong
theoretical prior observationally. These results can be used to determine the
robustness of our present knowledge when compared with forthcoming precision
data from Planck.
