Mirror Thermodynamic Bethe Ansatz for AdS3/CFT2

TL;DR

The paper tackles the exact non-perturbative finite-volume spectrum of strings on AdS3×S3×T4 with pure RR flux by formulating a canonical mirror TBA based on a complete string hypothesis that includes massive and massless modes as well as auxiliary roots.A new set of dressing factors is employed to construct the mirror Bethe-Yang equations and their fusion, leading to a full, non-truncated TBA system and a corresponding Y-system that captures the intricate scattering of left, right, massless, and auxiliary excitations.The authors derive integral equations for all particle densities, present the ground-state TBA equations, and provide a simplified TBA framework that yields compact Y-system relations, enabling non-perturbative spectrum computations and potential cross-checks with perturbative results.The work paves the way for studying excited states via contour deformation, exploring both large and small tension limits, and motivates extensions to mixed-flux backgrounds and other AdS3/CFT2 setups, with prospects for connection to the quantum spectral curve.

Abstract

We consider superstrings on the pure-Ramond-Ramond $AdS_3\times S^3\times T^4$ background. Using the recently-proposed dressing factors for the worldsheet S matrix, we formulate the string hypothesis for the mirror Bethe-Yang equations, and use it to derive the canonical mirror thermodynamic Bethe ansatz (TBA) equations of the model. For the first time, these equations account for all massive and massless modes of the model, and do not resort to any limit or special kinematics. We also discuss the simplified mirror TBA equations and the Y-system of the model.