Lifting asymptotic degeneracies with the Mirror TBA

TL;DR

This paper investigates a hidden symmetry in the AdS_5 x S^5 string spectrum that causes degeneracies not predicted by the asymptotic Bethe ansatz, and explores how finite size corrections resolve this degeneracy.

Contribution

It introduces the role of the Mirror TBA in lifting asymptotic degeneracies caused by enhanced discrete symmetries in the spectrum.

Findings

Finite size corrections lift degeneracies predicted by asymptotic Bethe ansatz.

Mirror TBA explicitly demonstrates degeneracy lifting for specific states.

Enhanced discrete symmetry affects the spectrum beyond asymptotic predictions.

Abstract

We describe a qualitative feature of the AdS_5 x S^5 string spectrum which is not captured by the asymptotic Bethe ansatz. This is reflected by an enhanced discrete symmetry in the asymptotic limit, whereby extra energy degeneracy enters the spectrum. We discuss how finite size corrections should lift this degeneracy, through both perturbative (Luscher) and non-perturbative approaches (the Mirror TBA), and illustrate this explicitly on two such asymptotically degenerate states.