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arXiv · 2510.25688

Conformal Blocks in 2d Carrollian/Galilean CFTs and Excited State Entanglement Entropy

Peng-Xiang Hao·Shunta Takahashi
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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 (ETH). 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 $\Delta$ and charge $\xi$ of the boundary state to the mass $m$ and angular momentum $j$ of the dual spacetime, offering a powerful consistency check for the Flat/CCFT correspondence.

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Peng-Xiang Hao, Shunta Takahashi. 2025-10-29. Conformal Blocks in 2d Carrollian/Galilean CFTs and Excited State Entanglement Entropy. https://doi.org/10.1103/y1bj-4y4h

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