The Källén-Lehmann representation in de Sitter spacetime

Abstract

We study two-point functions of symmetric traceless local operators in the bulk of de Sitter spacetime. We derive the Källén-Lehmann spectral decomposition for any spin and show that unitarity implies its spectral densities are nonnegative. In addition, we recover the Källén-Lehmann decomposition in Minkowski space by taking the flat space limit. Using harmonic analysis and the Wick rotation to Euclidean Anti de Sitter, we derive an inversion formula to compute the spectral densities. Using the inversion formula, we relate the analytic structure of the spectral densities to the late-time boundary operator content. We apply our technical tools to study two-point functions of composite operators in free and weakly coupled theories. In the weakly coupled case, we show how the Källén-Lehmann decomposition is useful to find the anomalous dimensions of the late-time boundary operators. We also derive the Källén-Lehmann representation of two-point functions of spinning primary operators of a Conformal Field Theory on de Sitter.

63 pages + appendices, 10 figures

References in corpus (9)

• Holography from Conformal Field Theory
• Writing CFT correlation functions as AdS scattering amplitudes
• Spinning AdS Propagators
• The IR stability of de Sitter: Loop corrections to scalar propagators
• Analyticity and Unitarity for Cosmological Correlators
• de Sitter tachyons and related topics
• Tensors and Spinors in de Sitter Space
• (Non-)unitarity of strictly and partially massless fermions on de Sitter space
• Group Averaging of massless scalar fields in 1+1 de Sitter

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• Charged Loops at the Cosmological Collider with Chemical Potential
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• Quantum information and the C-theorem in de Sitter
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• Real-time observables in de Sitter thermodynamics
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