Monday 03 December 2018
from 13:15
to 14:15 at
132:028

Speaker :

Ricardo Ferreira (Nordita)

Abstract :

During the accelerated expansion of the universe scalar and tensor fluctuations are produced and stretched outside the Hubble horizon. At late times these modes become super soft and locally indistinguishable from a coordinate transformation. However, they break the de-Sitter symmetries and their cumulation causes the breakdown of perturbation theory on ultra large scales when t_dS -> R_dS*S_dS, the equivalent of the Page time in the black hole context.
In this talk I will overview the main causes and consequences of such IR effects. I'll also present a different perspective on such breakdown by relating it to the spontaneous breaking of the dS asymptotic symmetries, to Bogoliubov transformations and to large gauge transformations.
The connection to Bogoliubov transformations allow us to go beyond perturbation theory and derive probability distributions on the ultra large scales.