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 $\text{horizon}\ensuremath{\leftrightarrow}\text{horizon}$ problem into a pair of (more symmetric) $\text{horizon}\ensuremath{\leftrightarrow}\text{twistor}$ problems.
Highlights
We introduce a spinor-helicity formalism, which encodes the field data on a cosmological horizon
In field theory on flat spacetime, the S-matrix between past and future infinity is an object of fundamental importance
For massless theories such as Yang-Mills and general relativity (GR), the spinor-helicity formalism [1] has emerged as the ideal language [2] for studying the S-matrix
Summary
In field theory on flat spacetime, the S-matrix between past and future infinity is an object of fundamental importance. For massless theories such as Yang-Mills and general relativity (GR), the spinor-helicity formalism [1] has emerged as the ideal language [2] for studying the S-matrix (with the exception of some highly symmetric cases, in which twistor language is superior [3,4,5]). We encode the lightlike field data on a cosmological horizon in terms of spinor-helicity variables, equivalent to those introduced in [7] for the Poincare patch (see the constructions for anti-de Sitter, in the Poincare patch [9] and in stereographic coordinates [10]). Our formalism and result provide a plausible starting point for efficiently including the effects of interactions in future work
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