Probing de Sitter from the horizon
Mehrdad Mirbabayi, Flavio Riccardi

TL;DR
This paper explores the physics within a de Sitter static patch by analyzing horizon correlators, generalizing quasinormal spectra, and establishing a finite-temperature effective field theory with positivity constraints.
Contribution
It introduces a novel approach to probe de Sitter space using horizon correlators, extending quasinormal spectrum analysis and formulating a boundary-coupled EFT with unitarity-based positivity constraints.
Findings
Generalized quasinormal spectrum in interacting theories
Connected horizon correlators to spectral density in dS
Derived positivity constraints on EFT parameters
Abstract
In a QFT on de Sitter background, one can study correlators between fields pushed to the future and past horizons of a comoving observer. This is a neat probe of the physics in the observer's causal diamond (known as the static patch). We use this observable to give a generalization of the quasinormal spectrum in interacting theories, and to connect it to the spectral density that appears in the K\"all\'en-Lehmann expansion of dS correlators. We also introduce a finite-temperature effective field theory consisting of free bulk fields coupled to a boundary. In matching it to the low frequency expansion of correlators, we find positivity constraints on the EFT parameters following from unitarity.
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Taxonomy
TopicsBlack Holes and Theoretical Physics · Cosmology and Gravitation Theories · Quantum Electrodynamics and Casimir Effect
