Seminarium "High Energy, Cosmology and Astro-particle Physics (HECA)"

The same spectrum of curvature perturbations can be explained by many different models. We first show this degeneracy by introducing homospectral expansion histories, i.e. classes of different expansion histories producing the same spectrum. We then consider other types of degeneracy associated to systems having the same momentum effective sound speed (MESS) of comoving curvature cosmological perturbations, which can be used to perform model independent analysis of observational data, or to define effective theories for different systems such as mutifields, modified gravity or super-gravity. As an application we show how the MESS can be used to obtain single field effective theories for some multifields inflationary models, and how it can be useful to compare different systems in terms of a unifying approach.

https://us02web.zoom.us/j/85478248551