Notes on conformal integrals: Coulomb branch amplitudes, magic identities and bootstrap

TL;DR

This paper investigates multi-loop conformal integrals in planar ${\cal N}=4$ super-Yang-Mills theory, deriving new identities, predicting integrand structures, and applying bootstrap methods to compute complex integrals relevant to Coulomb branch amplitudes.

Contribution

It introduces new magic identities among conformal integrals, summarizes all-loop integrand predictions, and develops a bootstrap approach for higher-loop integrals in the Coulomb branch.

Findings

Derived new zero-evaluation identities for conformal integrals.

Successfully bootstrapped four-loop integrals as weight-8 harmonic polylogarithms.

Computed leading singularities and partial functions for five-loop integrals.

Abstract

We study multi-loop conformal integrals for four-point correlators of planar ${\cal N}=4$ super-Yang-Mills theory, and in particular those contributing to Coulomb branch amplitudes in the ten-dimensional lightlike limit, where linear combinations of such integrals are determined by the large R-charge octagons exactly known from integrability. Exploiting known results for integrands, we review those combinations of dual conformal invariant (DCI) integrals that must evaluate to determinants of ladders, generalizing the simplest cases of Basso-Dixon fishnet integrals; in this way, we summarize all-loop predictions for the integrands (which are extracted from $f$-graphs) contributing to components of Coulomb branch amplitudes, such as next-to-fishnet integrals. Moreover, this exercise produces new ``magic identities", {\it i.e.} certain combinations of DCI integrals equal zero, and we enumerate and simplify such identities up to six loops explicitly. On the other hand, most of these individual integrals have not been computed beyond three loops, and as a first step we consider a bootstrap program for DCI integrals based on their leading singularities and the space of pure functions. We bootstrap the $3$ non-trivial DCI integrals for four-loop Coulomb branch amplitudes (providing an independent verification of the four-loop magic identity), which all take remarkably simple form as weight-$8$ single-valued harmonic polylogarithms. We also compute all leading singularities and a large portion of the pure functions for the $34$ DCI integrals contributing to five-loop amplitudes, where not only some integrals evaluate to functions beyond harmonic polylogarithms but they also contain lower-weight pieces individually.