WMAP and inflation

We assay how inflationary models whose properties are dominated by the dynamics of a single scalar field are constrained by cosmic microwave background (CMB) data from the Wilkinson Microwave Anisotropy Probe (WMAP). We classify inflationary models in a plane defined by the horizon-flow parameters. Our approach differs from that of the WMAP Collaboration in that we analyze only WMAP data and take the spectral shapes from slow-roll inflation rather than power-law parameterizations of the spectra. The only other information we use is the measurement of h from the Hubble Space Telescope (HST) Key Project. We find that the spectral index of primordial density perturbations lies in the 1sigma range 0.94 less than or equal to n(s) less than or equal to 1.04 with no evidence of running. The ratio of the amplitudes of tensor and scalar perturbations is smaller than 0.61 and the inflationary scale is below 2.8 x 10(16) GeV, both at the 2sigma C.L. No class of inflation or ekpyrotic/cyclic model is excluded. The lambdaphi(4) potential is excluded at 3sigma only if the number of e-folds is assumed to be less than 45. (C) 2003 Published by Elsevier B.V.