#### 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.