Theory Seminar Dong-Gang Wang

Cosmic inflation, which successfully describes the beginning of our Universe, can also be seen as a natural physics laboratory at extremely high energy scales. From the perspective of fundamental realizations, the low-energy effective theories of inflation are typically associated with a curved field manifold, which has drawn a lot of attention recently. One generic question is whether there exists any observational signatures of the inflationary curved field space. In this talk, after discussing several specific multi-field constructions, I will attack the above question in the context of "quasi-single field inflation / cosmological collider physics", where the extra fields have masses around the Hubble scale and lead to unique predictions in primordial non-Gaussianity. The analysis is performed by using both the multi-field approach and the background effective field theory of inflation, and we explicitly bridge the gap between these two equivalent descriptions. Here due to the curved field space, the standard “collider” signals in the squeezed bispectrum are modified, and a resulting running index directly measures the curvature of the internal field space. Therefore, this new phenomenology in non-Gaussianity may serve as a model-independent way to detect the field space geometry of inflation.