In this talk, I will present a novel geometric method to obtain the open system dynamics of a localised observer in de Sitter spacetime. This dynamics is encoded in a Schwinger-Keldysh effective action that describes the observer's radiation reaction as well as fluctuations associated with de Sitter Hawking radiation. I will discuss the computation of such an action for observers coupled to scalar and electromagnetic fields. We will find that the action provides a Langevin description of the observer at cosmologically long time-scales, whereas the near-flat space expansion reproduces the Abraham-Lorentz-Dirac force with cosmological corrections. On our way to understanding these results, we will also discuss scalar and electromagnetic multipole moments, a modified post-Newtonian expansion in the presence of a cosmological constant, and some new results about vector spherical harmonics on arbitrary dimensional spheres.
Zoom link: https://icts-res-in.zoom.us/j/94625768077?pwd=b5GpVhmIWkvyek4feNUNCZyRwrNNlZ.1
Meeting ID: 946 2576 8077
Passcode: 202030