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  • Open Access

K points and type IIB/heterotic duality with NS5-branes

Jeroen Monnee1, Timo Weigand1,2, and Max Wiesner1,*

  • *Contact author: max.wiesner@desy.de
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Phys. Rev. D 113, 066002 – Published 4 March, 2026

DOI: https://doi.org/10.1103/kcbz-jf16

Abstract

We revisit type II0 limits in the vector multiplet moduli space of compactifications of type IIB string theory on Calabi-Yau threefolds. These limits are special because they cannot be described using mirror symmetry. While we showed in previous work that the gravitational duality sector emerging in such limits corresponds to a weakly coupled heterotic string compactified on K3 times a string-sized torus, our focus here is on the additional field theory sectors that decouple from gravity in these asymptotic regimes. Concretely, we argue that, in the dual heterotic description, these field theory sectors correspond to spacetime-filling NS5-branes wrapping the heterotic torus. The existence of such nonperturbative field theory sectors manifests itself in an exponential dependence of the prepotential on the heterotic dilaton at leading order. Applied to K-point limits in one-parameter moduli spaces, our results imply that these limits are in perfect agreement with the distance and emergent string conjectures. More precisely, the light tower of states predicted by the distance conjecture arises from excitations of a weakly coupled heterotic string compactified to four dimensions on a background containing spacetime-filling NS5-branes.

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Phys. Rev. D 113, 066002– Published 4 March, 2026
  • Received 15 January 2026
  • Accepted 12 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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