Strings on NS-NS Backgrounds as Integrable Deformations

TL;DR

This work analyzes strings on AdS3 x S3 x T4 with NS-NS flux in uniform light-cone gauge and demonstrates that the worldsheet S matrix is a CDD factor between opposite chiralities, yielding a Bethe Ansatz akin to spin chains. The spectrum, including non-protected states, is reproduced from a WZW based construction and matches tree-level perturbative results, suggesting the NS-NS background is an integrable deformation of a free theory similar to TTbar. A key insight is that the T4 sector behaves as a free system with a state dependent worldsheet length, while SUSY ensures wrapping corrections cancel, making the Bethe-Yang equations exact. The analysis points to a broader program of understanding NS-NS backgrounds via simple integrable models and motivates extensions to other AdS3 geometries and nontrivial flux mixtures.

Abstract

We consider the worldsheet S matrix of superstrings on an AdS3xS3xT4 NS-NS background in uniform light-cone gauge. We argue that scattering is given by a CDD factor that is non-trivial only between opposite-chirality particles, yielding a spin-chain-like Bethe Ansatz. Our proposal reproduces the spectrum of non-protected states computed from the Wess-Zumino-Witten description and the perturbative tree-level S matrix. This suggests that the model is an integrable deformation of a free theory similar to those arising from the T-Tbar composite operator.