On the Quantum Spectral Curve for $\text{AdS}_3\times \text{S}^3\times \text{S}^3\times \text{S}^1$ strings and the $\mathfrak{d}(2,1;α)$ Q-system

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Main Authors: Cavaglià, Andrea, Frassek, Rouven, Primi, Nicolò, Tateo, Roberto
Format: Preprint
Published: 2025
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author Cavaglià, Andrea
Frassek, Rouven
Primi, Nicolò
Tateo, Roberto
author_facet Cavaglià, Andrea
Frassek, Rouven
Primi, Nicolò
Tateo, Roberto
contents In this paper, we put forward and discuss a proposal for a Quantum Spectral Curve (QSC) describing the planar spectrum of the holographic CFT dual to strings on AdS$_3\times$ S$^3\times$ S$^3\times$ S$^1$, a theory with global symmetry $\mathfrak{d}(2,1;α)^{\oplus 2}$. We focus mainly on the case when the radii of the two spheres are the same, i.e. $α= 1/2$, where the symmetry reduces to $\mathfrak{osp}(4|2)^{\oplus 2}$. In this case, our proposal is based on two copies of an $\mathfrak{osp}(4|2)$ Q-system, glued through the branch cuts of the Q-functions in a minimal way. We study in detail the ensuing analytic properties of the Q-functions in this proposal. Focusing on purely massive excitations, we consider the large worldsheet limit in which the QSC leads to a set of Asymptotic Bethe Ansatz (ABA) equations, yielding strong constraints on the (so-far unfixed) dressing factors of the worldsheet S-matrix. In a $\mathbb{Z}_2$-symmetric sector, our proposal is consistent with all previous results on the worldsheet S-matrix. However, in the non-symmetric case, we found a subtle incompatibility between the analytic constraints arising from the proposed QSC, the crossing equations present in the literature, and braiding unitarity. We discuss possible explanations for this mismatch: either our minimal QSC proposal does not hold beyond the symmetric sector, or the crossing unitarity equations receive a nontrivial correction that needs to be understood. Finally, we also propose a generalisation of the Q-system for the case of $α\neq 1/2$, corresponding to the superalgebra $\mathfrak{d}(2,1;α)$. This novel algebraic structure represents a significant step towards understanding the Quantum Spectral Curve of the entire theory.
format Preprint
id arxiv_https___arxiv_org_abs_2511_09635
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the Quantum Spectral Curve for $\text{AdS}_3\times \text{S}^3\times \text{S}^3\times \text{S}^1$ strings and the $\mathfrak{d}(2,1;α)$ Q-system
Cavaglià, Andrea
Frassek, Rouven
Primi, Nicolò
Tateo, Roberto
High Energy Physics - Theory
Exactly Solvable and Integrable Systems
In this paper, we put forward and discuss a proposal for a Quantum Spectral Curve (QSC) describing the planar spectrum of the holographic CFT dual to strings on AdS$_3\times$ S$^3\times$ S$^3\times$ S$^1$, a theory with global symmetry $\mathfrak{d}(2,1;α)^{\oplus 2}$. We focus mainly on the case when the radii of the two spheres are the same, i.e. $α= 1/2$, where the symmetry reduces to $\mathfrak{osp}(4|2)^{\oplus 2}$. In this case, our proposal is based on two copies of an $\mathfrak{osp}(4|2)$ Q-system, glued through the branch cuts of the Q-functions in a minimal way. We study in detail the ensuing analytic properties of the Q-functions in this proposal. Focusing on purely massive excitations, we consider the large worldsheet limit in which the QSC leads to a set of Asymptotic Bethe Ansatz (ABA) equations, yielding strong constraints on the (so-far unfixed) dressing factors of the worldsheet S-matrix. In a $\mathbb{Z}_2$-symmetric sector, our proposal is consistent with all previous results on the worldsheet S-matrix. However, in the non-symmetric case, we found a subtle incompatibility between the analytic constraints arising from the proposed QSC, the crossing equations present in the literature, and braiding unitarity. We discuss possible explanations for this mismatch: either our minimal QSC proposal does not hold beyond the symmetric sector, or the crossing unitarity equations receive a nontrivial correction that needs to be understood. Finally, we also propose a generalisation of the Q-system for the case of $α\neq 1/2$, corresponding to the superalgebra $\mathfrak{d}(2,1;α)$. This novel algebraic structure represents a significant step towards understanding the Quantum Spectral Curve of the entire theory.
title On the Quantum Spectral Curve for $\text{AdS}_3\times \text{S}^3\times \text{S}^3\times \text{S}^1$ strings and the $\mathfrak{d}(2,1;α)$ Q-system
topic High Energy Physics - Theory
Exactly Solvable and Integrable Systems
url https://arxiv.org/abs/2511.09635