Abstract

A well-established result in QFT in four-dimensional de Sitter spacetime states that the vacuum of a massless scalar field lacks a normalizable inner product. This has often been interpreted as evidence that the vacuum cannot remain invariant under the full de Sitter isometry group, suggesting the emergence of time-dependent (secular) growth in correlation functions computed in inflationary coordinates. However, the standard quantization of scalar fields in de Sitter spacetime using inflationary coordinates yields a vacuum state for the massless scalar field that explicitly preserves de Sitter symmetries, albeit with infrared divergences. In this talk, I will discuss the computation of n-point correlation functions and demonstrate that loop corrections do not further enhance the secular growth of these functions for massless scalars. I will also address the discrepancies between our findings and those reported in previous studies.