Short Strings in Three-Dimensional Anti-de Sitter Space: from Weak to Strong Coupling
Simon Ekhammar, Nikolay Gromov, Bogdan Stefański, Charles Thull
TL;DR
This work delivers the first nonperturbative spectral results for strings on AdS$_3\times$S$^3\times$T$^4$ with RR flux by solving the conjectured AdS$_3$ QSC across the full coupling range. It demonstrates a seamless connection between a weak-coupling, spin-chain description and a strong-coupling, string-theoretic regime, where energies organize into flat-space Regge trajectories with KK-induced splittings; the leading strong-coupling scaling is $oldsymbol{\Delta}\sim 2\sqrt{\delta}\,\lambda_h^{1/4}$ with $E_0=0$ and a nonvanishing $E_2$, while subleading weak-coupling corrections arise from a nearest-neighbour $\mathfrak{sl}_2$ spin-chain with wrapping at $\mathcal{O}(h^3)$. The authors develop a convergence-accelerated numerical approach based on polylogarithmic bases to extract precise $\Delta(h)$, validate the results against classical folded-string predictions, and compare with AdS$_3$ Virasoro–Shapiro amplitudes. These results provide concrete spectral data across moduli space, enabling precision holography in AdS$_3$ and offering a platform to test related amplitudes and thermodynamic formulations in RR backgrounds. The work thus offers a quantitative bridge between integrability techniques and stringy dynamics in AdS$_3$ holography, with clear directions for extending to massless modes, mixed flux, and higher-dimensional AdS/CFT settings.
Abstract
We numerically solve the conjectured Quantum Spectral Curve for strings on AdS$_3\times$S$^3\times$T$^4$ with R--R charge from weak to strong coupling. At strong coupling, the spectrum organises into flat-space string mass levels with universal square-root scaling in the string tension at leading order, and additional Kaluza-Klein fine-splitting at subleading order. At weak coupling, the energies are determined by a nearest-neighbour Bethe Ansatz, with universal subleading corrections that are suppressed at large volume.
