Little String Amplitudes (and the Unreasonable Effectiveness of 6D SYM)

TL;DR

This paper compares tree-level amplitudes in little string theory with loop amplitudes in 6D super-Yang-Mills, revealing striking agreements and insights into UV divergences.

Contribution

It provides a detailed comparison between little string amplitudes and 6D SYM loop amplitudes, highlighting unexpected agreements and implications for UV behavior.

Findings

Striking agreement between little string and 6D SYM amplitudes up to 2 loops

Numerical evaluation of conformal block integrals in alpha' expansion

Discussion on UV divergence issues at higher loops in gauge theory

Abstract

We study tree level scattering amplitudes of four massless states in the double scaled little string theory, and compare them to perturbative loop amplitudes in six-dimensional super-Yang-Mills theory. The little string amplitudes are computed from correlators in the cigar coset CFT and in N=2 minimal models. The results are expressed in terms of integrals of conformal blocks and evaluated numerically in the alpha' expansion. We find striking agreements with up to 2-loop scattering amplitudes of massless gluons in 6D SU(k) SYM at a Z_k invariant point on the Coulomb branch. We comment on the issue of UV divergence at higher loop orders in the gauge theory and discuss the implication of our results.