2003/08/31 by Kevin Goldstein, David A. Lowe
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Quantum Electrodynamics and Casimir Effect #hep-th
paper · pdf · doi:10.1103/physrevd.69.023507
published as Phys.Rev. D69 (2004) 023507 · 18 pages, 3 figures, RevTex, some references added, minor corrections
arxiv created 2003/12/03 · openalex publication_date 2004/01/29 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider scalar field theory in de Sitter space with a general vacuum invariant under the continuously connected symmetries of the de Sitter group. We begin by reviewing approaches to define this as a perturbative quantum field theory. One approach leads to Feynman diagrams with pinch singularities in the general case, which renders the theory perturbatively ill defined. Another approach leads to well-defined perturbative correlation functions on the imaginary time continuation of de Sitter space. When continued to real time, a path integral with a non-local action generates the time-ordered correlators. Curiously, observables built out of local products of the fields show no sign of this nonlocality. However, once one couples to gravity, we show acausal effects are unavoidable and presumably make the theory ill defined. The Bunch-Davies vacuum state is the unique de Sitter invariant state that avoids these problems.