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  • Open Access

Conformal blocks in 2D Carrollian-Galilean CFTs and excited state entanglement entropy

Peng-Xiang Hao*

Shunta Takahashi†

  • *Contact author: pxhao@yukawa.kyoto-u.ac.jp
  • †Contact author: shunta@gauge.scphys.kyoto-u.ac.jp
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Phys. Rev. D 113, 106014 – Published 15 May, 2026

DOI: https://doi.org/10.1103/y1bj-4y4h

Abstract

We advance the study of flat space holography by computing the entanglement entropy of highly excited states in two-dimensional Carrollian/Galilean Conformal Field Theories (C/G CFTs). Our approach is centered on a novel, physically intuitive derivation of the heavy-light conformal block in the large central charge limit, where the backreaction of heavy operators is absorbed by a C/G conformal coordinate transformation. Using this result and the replica trick, we find that the entanglement entropy of highly excited states assumes a thermal form, providing a concrete realization of the eigenstate thermalization hypothesis. This field-theoretic result perfectly reproduces the holographic entanglement entropy computed via the swing surface proposal in three-dimensional Einstein gravity, for backgrounds corresponding to spinning particles and flat space cosmological solutions. This agreement establishes a precise dictionary relating the weight Δ and charge ξ of the boundary state to the mass m and angular momentum j of the dual spacetime, offering a powerful consistency check for the Flat/Carrollian conformal field theory correspondence.

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Phys. Rev. D 113, 106014– Published 15 May, 2026
  • Received 23 February 2026
  • Accepted 17 April 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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