April 17, 10:15 in E204   

Matti Savelainen (Helsinki)


WMAP7 CMB data constraints on two-field inflation

We obtain constraints on scalar and tensor perturbations in phenomenological and two-field inflation models. We calculate the Bayesian evidences for primordial isocurvature and tensor modes. We focus on cold dark matter (CDM) and baryon isocurvature perturbations and study what information currently available data on the cosmic microwave background give on possible deviations from adiabaticity. We check how the results change if we add supernova or large-scale structure (that includes baryon acoustic oscillations, BAO) data into the analysis. We allow for the presence of tensor perturbations. We assume a powerlaw power spectrum for the primordial curvature and entropy perturbations and allow or correlations between them. We use two different approaches: 1) A phenomenological approach, where we make no reference to the origin of the primordial perturbations, and just try to determine or constrain their amplitudes and spectral indices from the data. 2) A slowroll two-field inflation approach, where we assume the perturbations were generated by quantum fluctuations during two-field inflation, and the spectral indices are determined by the slow-roll parameters at the time the cosmological scales exited horizon during inflation. Assuming spatially flat geometry of the Universe, we perform full parameter scans of this mixed (adiabatic and isocurvature) model, as well as the standard pure adiabatic CDM model for comparison. We present posterior probability densities of the standard cosmological parameters and the extra isocurvature parameters, and report the Bayesian evidences for these models calculated with the MultiNest nested sampling package using the CMB data alone or CMB data combined with other data sets. For the references see ArXiv:1202.2852.