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Analytic approach to boundary integrability with application to mixed-flux AdS3×S3

Julio Cabello Gil1,2,* and Sibylle Driezen1,†

  • *Contact author: cabelloj@physik.hu-berlin.de
  • †Contact author: sdriezen@phys.ethz.ch
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Phys. Rev. D 114, 086017 – Published 26 October, 2026

DOI: https://doi.org/10.1103/vrh4-v4nl

Abstract

Boundary integrability provides rare analytic control over field theories with interfaces, from quantum impurity problems to open string dynamics. We propose a new approach for integrable boundaries in two-dimensional sigma models that uses the divisor structure of the Lax connection to identify admissible reflection maps, including when standard parity-based constructions fail. Applied to open strings on AdS3×S3 with mixed Neveu-Schwarz–Neveu-Schwarz–Ramond-Ramond flux, where the Neveu-Schwarz–Neveu-Schwarz flux breaks world sheet parity, we find two interesting branches of integrable boundaries: one restricted to pure Ramond-Ramond flux and another admitting D-branes wrapping twisted conjugacy classes for generic flux. At the Wess-Zumino-Witten point, the latter reduces to the known conformal D-branes, opening a path to comparison with conformal perturbation theory. More broadly, our framework suggests generalizations of standard lattice constructions that may enlarge existing classifications of integrable boundaries.

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Phys. Rev. D 114, 086017– Published 26 October, 2026
  • Received 12 March 2026
  • Accepted 5 October 2026
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