Theory HEP Seminar

Transient reductions of the inflaton speed of sound in the Cosmic Microwave Background<

Ana Achucarro

Institute Lorentz for Theoretical Physics
Leiden University

The first year of observations by the Planck satellite mission shows that the cosmic microwave background (CMB) fluctuations are consistent with gaussian statistics in the primordial perturbations, a key prediction of the simplest models of inflation. However, there are hints of anomalies in the CMB power spectrum and bispectrum. We consider the possibility that some of these anomalous features have a common physical origin in a transient reduction of the inflaton speed of sound (for instance, but not only, resulting from a turn in the inflationary trajectory). We do this by exploiting predicted correlations between the power spectrum and bispectrum, which I will explain, as well as some recent theoretical developments in the effective field theory of inflationary perturbations. Our results strongly suggest that current data might already be sensitive enough to detect transient reductions in the speed of sound as mild as a few percent. Since this is a signature of interactions, it opens a new window for the detection of extra degrees of freedom during inflation.

[Based on arXiv:1311.2552 and earlier work starting with arXiv:1010.3693.]