Abstract

The field of primordial non-Gaussianities is twenty years old. During that time, cosmologists have built a dictionary between the physics active during inflation and higher-order correlation functions of primordial density fluctuations. I will argue that this dictionary is far from complete, with theoretical predictions available only in restricted classes of theories. To fill in this gap, I will present the cosmological flow, a complete and systematic approach to compute inflationary correlators for all inflationary theories. This enables to assist our theoretical understanding and to generate theoretical data for an unbiased interpretation of upcoming cosmological observations. I will explain that the cosmological collider signal, lying in soft limits of correlators, often described as a robust probe of the field content of inflation, is as robust as its assumptions are restrictive, and I will show its properties in theories involving multiple degrees of freedom, with strong mixing, and in the presence of features. Eventually, I will describe the low speed collider signal, a recently identified signature of heavy fields characterised by peculiar resonances in soft limits, and which can be understood in terms of a non-local single-field effective field theory.