Abstract.
I will start with a general introduction to the long ongoing discussion regarding infrared divergencies in de Sitter, the physical nature of soft graviton modes, and the relation to cosmology. After this introduction, I will discuss my recent work showing how soft graviton modes in de Sitter can be viewed as the Goldstone modes of the spontaneously broken asymptotic symmetry group of de Sitter. I then show that any local measurement, including the effects of the environment, will collapse the symmetric state onto the broken state in the large volume limit. In any discussion involving observers, de Sitter is, therefore, best described globally by the broken phase. In contrast, local observers, in the small volume limit, cannot discriminate between different degenerate global vacuum states and are, therefore, best described by the symmetric state. In this picture, the Page time of de Sitter can be viewed as the time scale after which a local volume has inflated to a size where it can no longer be described by the symmetric state.
(The slides will be available here)