# Patient Observers and Non-perturbative Infrared Dynamics in Inflation

## TL;DR

This paper explores the impact of soft graviton modes on de Sitter quantum states, using Bogoliubov transformations to analyze observability, and proposes a non-perturbative framework to understand eternal inflation.

## Contribution

It introduces a novel non-perturbative approach to relate quantum states with and without soft modes in de Sitter space, addressing observability and eternal inflation criteria.

## Key findings

- Soft graviton effects can be related to particle production via Bogoliubov transformations.
- Quantum uncertainties may limit the local measurability of infrared effects.
- A new criterion for eternal inflation based on quantum state distributions is proposed.

## Abstract

We have previously derived the effect of soft graviton modes on the quantum state of de Sitter using spontaneously broken asymptotic symmetries. In the present paper we reinterpret this effect in terms of particle production and relate the quantum states with and without soft modes by means of Bogoliubov transformations. This also enables us to address the much discussed issues regarding the observability of infrared effects in de Sitter from a new perspective. While it is commonly agreed that infrared effects are not visible to a single sub-horizon observer at late times, we argue that the question is less trivial for a {\it patient observer} who has lived long enough to have a record of the state before the soft mode was created. Though classically there is no obstruction to measuring this effect locally, we give several indications that quantum mechanical uncertainties may censor the effect. We then apply our methods to find a non-perturbative description of the quantum state pertaining to the Page time of de Sitter, and derive with these new methods the probability distribution for the local quantum states of de Sitter and slow-roll inflation in the presence of long modes. Finally, we use this to formulate a precise criterion for the existence of eternal inflation in general classes of slow-roll inflation.