Limits on defects formation and hybrid inflationary models with three-year WMAPobservations

Abstract

We confront the predicted effects of hybrid inflationary models on the Cosmic MicrowaveBackground (CMB) with three years of Wilkinson Microwave Anisotropy Probe (WMAP)observations. Using model selection, we compare the ability of a simple flat power-lawΛCDM model to describe the data to that of hybrid inflationary models involving global or localcosmic strings, or global textures. We find that it is statistically impossible todistinguish between these models: they all give a similar description of the data, themaximum ratio of the various Bayesian evidences involved being never higher thane0.1 ± 0.5. We then derive the maximum contribution that topological defects can make to the CMB,and place an upper bound on the possible value of cosmic strings’ tension ofGμ ≤ 2.1 × 10−7 (68% confidence limit). Finally, we give the corresponding constraints on the D-termstrings’ mass scale, as well as limits on the F- and D-term coupling constants(κ andλ) and inflationaryscales (M and ).