Taming the $\epsilon$-expansion with Large Spin Perturbation Theory

TL;DR

This paper uses analytic bootstrap and large spin perturbation theory to compute CFT data in the Wilson-Fisher model up to fourth order in epsilon, providing a systematic approach to understanding operator dimensions and OPE coefficients.

Contribution

It introduces a method combining crossing symmetry and large spin perturbation theory to determine CFT data at higher orders in epsilon expansion.

Findings

Computed anomalous dimensions and OPE coefficients up to fourth order in epsilon.

Simplified calculations at cubic order due to limited contributions to double discontinuity.

Proposed a structure of functions with fixed transcendentality for higher-order corrections.

Abstract

We apply analytic bootstrap techniques to the four-point correlator of fundamental fields in the Wilson-Fisher model. In an $\epsilon$-expansion crossing symmetry fixes the double discontinuity of the correlator in terms of CFT data at lower orders. Large spin perturbation theory, or equivalently the recently proposed Froissart-Gribov inversion integral, then allows one to reconstruct the CFT data of intermediate operators of any spin. We use this method to compute the anomalous dimensions and OPE coefficients of leading twist operators. To cubic order in $\epsilon$ the double discontinuity arises solely from the identity operator and the scalar bilinear operator, making the computation straightforward. At higher orders the double discontinuity receives contributions from infinite towers of higher spin operators. At fourth order, the structure of perturbation theory leads to a proposal in terms of functions of certain degree of transcendentality, which can then be fixed by symmetries. This leads to the full determination of the CFT data for leading twist operators to fourth order.