Description
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). This setup highlights how the analytic structure of de Sitter correlators encodes a generalized quasinormal spectrum, even in interacting theories, using the analyticity properties of the spectral density that appears in the Källén-Lehmann expansion of dS correlators. I will also show how the low-frequency behaviour is captured by a finite-temperature EFT with boundary couplings, leading to unitarity constraints on the EFT parameters. Understanding these analytic properties offers new tools for going beyond conventional perturbation theory in the study of inflationary correlators.
