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- Title
De Sitter diagrammar and the resummation of time.
- Authors
Baumgart, Matthew; Sundrum, Raman
- Abstract
Light scalars in inflationary spacetimes suffer from logarithmic infrared divergences at every order in perturbation theory. This corresponds to the scalar field values in different Hubble patches undergoing a random walk of quantum fluctuations, leading to a simple toy "landscape" on superhorizon scales, in which we can explore questions relevant to eternal inflation. However, for a sufficiently long period of inflation, the infrared divergences appear to spoil computability. Some form of renormalization group approach is thus motivated to resum the log divergences of conformal time. Such a resummation may provide insight into De Sitter holography. We present here a novel diagrammatic analysis of these infrared divergences and their resummation. Basic graph theory observations and momen- tum power counting for the in-in propagators allow a simple and insightful determination of the leading-log contributions. One thus sees diagrammatically how the superhorizon sector consists of a semiclassical theory with quantum noise evolved by a first-order, interacting classical equation of motion. This rigorously leads to the "Stochastic Inflation" ansatz developed by Starobinsky to cure the scalar infrared pathology nonperturbatively. Our approach is a controlled approximation of the underlying quantum field theory and is systematically improvable.
- Subjects
HUBBLE Space Telescope (Spacecraft); QUANTUM field theory; QUANTUM fluctuations; RENORMALIZATION group; QUANTUM theory; INFLATIONARY universe; QUANTUM noise; RANDOM walks
- Publication
Journal of High Energy Physics, 2020, Vol 2020, Issue 7, pN.PAG
- ISSN
1126-6708
- Publication type
Article
- DOI
10.1007/JHEP07(2020)119