Conformal Field Theories in Six-Dimensional Twistor Space

TL;DR

This paper explores the six-dimensional twistor space and Penrose transform, establishing new methods for representing massless fields and their applications to conformal field theories and amplitude calculations.

Contribution

It provides a novel construction of the twistor transform in six dimensions, extending Sparling's -transform, and develops tools for conformal field theories in twistor space.

Findings

Proves surjectivity of the Penrose transform in 6D.

Extends Sparling's -transform to all helicities.

Analyzes conformally invariant ^3 amplitude in twistor space.

Abstract

This article gives a study of the higher-dimensional Penrose transform between conformally invariant massless fields on space-time and cohomology classes on twistor space, where twistor space is defined to be the space of projective pure spinors of the conformal group. We focus on the 6-dimensional case in which twistor space is the six-quadric Q in CP^7 with a view to applications to the self-dual (0,2)-theory. We show how spinor-helicity momentum eigenstates have canonically defined distributional representatives on twistor space (a story that we extend to arbitrary dimension). These give an elementary proof of the surjectivity of the Penrose transform. We give a direct construction of the twistor transform between the two different representations of massless fields on twistor space (H^2 and H^3) in which the H^3s arise as obstructions to extending the H^2s off Q into CP^7. We also develop the theory of Sparling's `\Xi-transform', the analogous totally real split signature story based now on real integral geometry where cohomology no longer plays a role. We extend Sparling's \Xi-transform to all helicities and homogeneities on twistor space and show that it maps kernels and cokernels of conformally invariant powers of the ultrahyperbolic wave operator on twistor space to conformally invariant massless fields on space-time. This is proved by developing the 6-dimensional analogue of the half-Fourier transform between functions on twistor space and momentum space. We give a treatment of the elementary conformally invariant \Phi^3 amplitude on twistor space and finish with a discussion of conformal field theories in twistor space.