# Spinor-helicity variables for cosmological horizons in de Sitter space

## TL;DR

This paper introduces a spinor-helicity formalism for massless fields in de Sitter space, simplifying the evolution of free fields across cosmological horizons using twistor theory and Fourier transforms.

## Contribution

It develops a novel spinor-helicity approach for de Sitter horizons, connecting horizon data to twistor theory and simplifying the horizon-to-horizon evolution of massless fields.

## Key findings

- Reduces horizon evolution to a Fourier transform.
- Connects horizon data with twistor theory.
- Provides a new formalism for massless fields in de Sitter space.

## Abstract

We consider massless fields of arbitrary spin in de Sitter space. We introduce a spinor-helicity formalism, which encodes the field data on a cosmological horizon. These variables reduce the free S-matrix in an observer's causal patch, i.e. the evolution of free fields from one horizon to another, to a simple Fourier transform. We show how this result arises via twistor theory, by decomposing the horizon<->horizon problem into a pair of (more symmetric) horizon<->twistor problems.