Non-locality in Quantum Field Theory due to General Relativity

TL;DR

This paper demonstrates that coupling General Relativity with quantum fields naturally induces non-local effects characterized by higher-dimensional operators, leading to small, typically unobservable non-Gaussianities in inflationary cosmology.

Contribution

It reveals the emergence of non-local effects with shift symmetry in quantum field theories coupled to gravity, and discusses their implications for inflationary models.

Findings

Non-local effects are generically produced by gravity-quantum field coupling.

These effects manifest as higher-dimensional operators with approximate shift symmetry.

Small non-Gaussianities are a common feature but remain observationally elusive.

Abstract

We show that General Relativity coupled to a quantum field theory generically leads to non-local effects in the matter sector. These non-local effects can be described by non-local higher dimensional operators which remarkably have an approximate shift symmetry. When applied to inflationary models, our results imply that small non-Gaussianities are a generic feature of models based on General Relativity coupled to matter fields. However, these effects are too small to be observable in the Cosmic Microwave Background.