Inflation model constraints from the Wilkinson Microwave Anisotropy Probe three-year data

Abstract

We extract parameters relevant for distinguishing among single-field inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data set, and also from WMAP in combination with the Sloan Digital Sky Survey (SDSS) galaxy power spectrum. Our analysis leads to the following conclusions: (1) the Harrison---Zel'dovich model is consistent with both data sets at a 95% confidence level; (2) there is no strong evidence for running of the spectral index of scalar perturbations; (3) potentials of the form $V\ensuremath{\propto}{\ensuremath{\phi}}^{p}$ are consistent with the data for $p=2$, and are marginally consistent with the WMAP data considered alone for $p=4$, but ruled out by WMAP combined with SDSS. We perform a ``Monte Carlo reconstruction'' of the inflationary potential, and find that: (1) there is no evidence to support an observational lower bound on the amplitude of gravitational waves produced during inflation; (2) models such as simple hybrid potentials which evolve toward an inflationary late-time attractor in the space of flow parameters are strongly disfavored by the data, (3) models selected with even a weak slow-roll prior strongly cluster in the region favoring a red power spectrum and no running of the spectral index, consistent with simple single-field inflation models.