Abstract

We argue that every CFT contains light-ray operators labeled by a continuous spin J. When J is a positive integer, light-ray operators become integrals of local operators over a null line. However for non-integer J , light-ray operators are genuinely nonlocal and give the analytic continuation of CFT data in spin described by Caron-Huot. A key role in our construction is played by a novel set of intrinsically Lorentzian integral transforms that generalize the shadow transform. Matrix elements of light-ray operators can be computed via the integral of a double-commutator against a conformal block. This gives a simple derivation of Caron-Huot’s Lorentzian OPE inversion formula and lets us generalize it to arbitrary four-point functions. Furthermore, we show that light-ray operators enter the Regge limit of CFT correlators, and generalize conformal Regge theory to arbitrary four-point functions. The average null energy operator is an important example of a light-ray operator. Using our construction, we find a new proof of the average null energy condition (ANEC), and furthermore generalize the ANEC to continuous spin.

Highlights

  • Singularities of Euclidean correlators in conformal field theory (CFT) are described by the operator product expansion (OPE)

  • We show that light-ray operators enter the Regge limit of CFT correlators, and generalize conformal Regge theory to arbitrary fourpoint functions

  • By expressing E as the residue of an integral of a pair of real operators φ(x1)φ(x2), we find a new proof of the average null energy condition (ANEC) in section 6.7 E is part of a family of light-ray operators EJ labeled by continuous spin J, and our construction of light-ray operators applies to this entire family

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Summary

Introduction

Singularities of Euclidean correlators in conformal field theory (CFT) are described by the operator product expansion (OPE). The analytic continuation of OPE data in a scalar four-point function φ1φ2φ3φ4 can be computed by a “Lorentzian inversion formula,” given by the integral of a doublecommutator [φ4, φ1][φ2, φ3] times a conformal block GJ+d−1,∆−d+1 with unusual quantum numbers. We generalize conformal Regge theory to arbitrary operator representations as well, along the way showing that light-ray operators describe part of the Regge limit of four-point functions as conjectured in [6]. By expressing E as the residue of an integral of a pair of real operators φ(x1)φ(x2), we find a new proof of the ANEC in section 6.7 E is part of a family of light-ray operators EJ labeled by continuous spin J, and our construction of light-ray operators applies to this entire family. (1.22) and (1.23) do not include OPE coefficients

The light transform
Review
Symmetry between different Poincare patches
Causal structure
Review: representation theory of the conformal group
Weyl reflections and integral transforms
Transform for L
Some properties of the light transform
Light transform of a Wightman function
Light transform of a time-ordered correlator
Algebra of integral transforms
Light-ray operators
Euclidean partial waves
Wick-rotation to Lorentzian signature
The light transform and analytic continuation in spin
Light-ray operators in Mean Field Theory
Subleading families and multi-twist operators
Lorentzian inversion formulae
The double commutator
Inversion for a four-point function of primaries
A natural formula for the Lorentzian block
Generalization to arbitrary representations
The generalized Lorentzian inversion formula
Proof using weight-shifting operators
Relation to light-ray operators
Positivity and the ANEC
Discussion
Full Text
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