2016/09/30 by Ricardo Z. Ferreira, McCullen Sandora, Martin S. Sloth
Physics and Astronomy · #Black Holes and Theoretical Physics #Boson #Classical mechanics #Cosmology and Gravitation Theories #De Sitter space #De Sitter universe #Goldstone boson #Gravitation #Graviton #Homogeneous space #Inflation (cosmology) #Mathematical physics #Particle physics theoretical and experimental studies #Physics #Quantum mechanics #Semiclassical physics #Spacetime #Theoretical physics #Universe #Vacuum state #astro-ph.CO #de Sitter invariant special relativity #gr-qc #hep-th
paper · pdf · doi:10.1088/1475-7516/2017/04/033
22 pages + appendices, 3 figures. V2: Typos fixed, references and clarifications added
arxiv created 2016/10/14 · openalex publication_date 2017/04/19 · arxiv updated 2017/04/26 · openalex created_date 2020/11/23 · openalex updated_date 2026/08/05
Soft gravitons produced by the expansion of de Sitter can be viewed as the Nambu-Goldstone bosons of spontaneously broken asymptotic symmetries of the de Sitter spacetime. We explicitly construct the associated charges, and show that acting with the charges on the vacuum creates a new state equivalent to a change in the local coordinates induced by the soft graviton. While the effect remains unobservable within the domain of a single observer where the symmetry is unbroken, this change is physical when comparing different asymptotic observers, or between a transformed and un-transformed initial state, consistent with the scale-dependent statistical anisotropies previously derived using semiclassical relations. We then compute the overlap, ⟨0| 0'⟩, between the unperturbed de Sitter vacuum |0⟩, and the state | 0'⟩ obtained by acting times with the charge. We show that when → M p 2 / H 2 this overlap receives order one corrections and 0⟨0| 0'⟩→ , which corresponds to an infrared perturbative breakdown after a time t dS ∼ M p 2 / H 3 has elapsed, consistent with earlier arguments in the literature arguing for a perturbative breakdown on this timescale. We also discuss the generalization to inflation, and rederive the 3-point and one-loop consistency relations.