Integrability and Transcendentality

TL;DR

This paper derives a two-loop Bethe ansatz for N=4 gauge theory, analyzes an all-loop asymptotic ansatz, and predicts a universal scaling function for large-spin operators, linking gauge theory and string theory results.

Contribution

It introduces a novel all-loop scaling function obeying transcendentality principles, connecting perturbative gauge theory with string theory predictions.

Findings

Derivation of the two-loop Bethe ansatz for sl(2) sector.

Proposal of a universal all-loop scaling function.

Qualitative agreement with string theory at strong coupling.

Abstract

We derive the two-loop Bethe ansatz for the sl(2) twist operator sector of N=4 gauge theory directly from the field theory. We then analyze a recently proposed perturbative asymptotic all-loop Bethe ansatz in the limit of large spacetime spin at large but finite twist, and find a novel all-loop scaling function. This function obeys the Kotikov-Lipatov transcendentality principle and does not depend on the twist. Under the assumption that one may extrapolate back to leading twist, our result yields an all-loop prediction for the large-spin anomalous dimensions of twist-two operators. The latter also appears as an undetermined function in a recent conjecture of Bern, Dixon and Smirnov for the all-loop structure of the maximally helicity violating (MHV) n-point gluon amplitudes of N=4 gauge theory. This potentially establishes a direct link between the worldsheet and the spacetime S-matrix approach. A further assumption for the validity of our prediction is that perturbative BMN (Berenstein-Maldacena-Nastase) scaling does not break down at four loops, or beyond. We also discuss how the result gets modified if BMN scaling does break down. Finally, we show that our result qualitatively agrees at strong coupling with a prediction of string theory.