Modular Hamiltonian and entanglement entropy in the BMS free fermion theory
Abstract
We study the modular Hamiltonian and the entanglement entropy of the BMS-invariant free fermion model. Starting from the modular Hamiltonian on a half-line interval, we calculate the modular Hamiltonian for a region consisting of two disjoint intervals using the uniformization map and a background field method. The resulting modular Hamiltonian contains a local term which generates a geometrical flow, and a bi-local term which mixes operators between the two intervals. We further derive a relation between Wightman functions and the modular Hamiltonian using both diagonalization and a coherent state method. This enables us to compute the entanglement entropy for multi-disjoint intervals. Our explicit results in the BMS free fermion model are compatible with earlier ones based on symmetry and holography.
Keywords
Cite
@article{arxiv.2507.10503,
title = {Modular Hamiltonian and entanglement entropy in the BMS free fermion theory},
author = {Peng-Xiang Hao and Wen-Xin Lai and Wei Song and Zehua Xiao},
journal= {arXiv preprint arXiv:2507.10503},
year = {2025}
}
Comments
36 pages, 4 figures