Observational Signatures of Multifield Inflation

Slow-roll single-field inflation constitutes the main paradigm of the Early Universe. But this model suffers from a number of conceptual issues that naturally lead to the consideration of multifield models of inflation with curved field space, which have recently been under scrutiny as realistic realisations of high-energy physics in the Early Universe. After reviewing famous multifield results, the speaker will show that the non-trivial internal geometry reshuffles observational predictions from inflation, at the level of the background (geometrical destabilisation of inflation), of linear fluctuations (spectral index, tensor-to-scalar ratio) and can lead to exotic type of non-Gaussianities (bispectrum, higher-order correlation functions). This last fact in particular motivates the thorough analysis of non-Gaussianities in this large class of models. For that, we revisit Maldacena's calculation of the bispectrum in a 2-field context.

As a byproduct, we also derive the corresponding effective single-field theory, when the fluctuation perpendicular to the trajectory (isocurvature mode) is heavy enough to be integrated out, and explicitly show the effect of the curvature of the field space on the bispectrum.

The seminar will take place on Friday 6 November 2020 at 12:00 (CEST).

If you are not an ICCUB member and would like to attend this activity, please send an email to Marija Tomasevic or Jairo Martínez.