Date:
25. September 2020 - 11:30
Speaker:
Lucas Pinol (Institut d’Astrophysique de Paris)
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, I 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 corresonding
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. Time permitting I will also mention other projects that might
interest the audience, such as multifield stochastic inflation and
multifield/multi-fluid reheating after inflation.