Speaker
Description
The generation of primordial density inhomogeneities from inflaton quantum fluctuations is a crucial prediction of inflation. The correlation functions of these fluctuations, called cosmological correlators, can be studied in a perturbative framework where the quantum fluctuations can be described as quantum fields that propagate in a de Sitter space-time. However, this propagation has a complex time and kinematic dependence due to broken Lorentz invariance.
In this talk, I will show how an integral transform allows one to express the mode functions that encode propagation of quantum fields in de Sitter in terms of their flat-space counterpart, which are plane waves. Then, this integral transform can be used to write any cosmological correlator from the corresponding flat-space one, by applying a suitable linear transform on the kinematic variables and integrating over the transformation variables. In particular, I will illustrate this construction with a fundamental example, that is the exchange of a single massive particle during inflation.