Abstract
We study the constraints on the inflationary parameter space derived from the 3year WMAP data set using ‘slow roll reconstruction’, using the SDSS galaxypower spectrum to gain further leverage where appropriate. This approach insertsthe inflationary slow roll parameters directly into a Monte Carlo Markov chainestimate of the cosmological parameters, and uses the inflationary flow hierarchy tocompute the parameters’ scale dependence. We work with the first three parameters(ϵ,η and ξ) and pay close attention to the possibility that the 3 year WMAP data setcontains evidence for a ‘running’ spectral index, which is dominated by theξ term. Mirroring the WMAP team’s analysis we find that the permitted distribution ofξ is broad, and centred away from zero. However, when we require thatinflationary parameters yield at least 30 additional e-folds of inflationafter the largest observable scales leave the horizon, the bounds onξ tighten dramatically. We make use of the absence of an explicit pivot scale in theslow roll reconstruction formalism to determine the dependence of the computedparameter distributions on the pivot. We show that the choice of pivot has asignificant effect on the inferred constraints on the inflationary variables, and thespectral index and running derived from them. Finally, we argue that the nextround of cosmological data can be expected to place very stringent constraints onthe region of parameter space open to single field models of slow roll inflation.
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