Work

Modular Hamiltonian and entanglement entropy in the BMS free fermion theory

Year: 2026

Type: article

Abstract: A bstract 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.

Source: Journal of High Energy Physics

DOI: 10.1007/jhep02(2026)099

Authors: Peng-Xiang Hao, Wen-Xin Lai, Wei Song, Zehua Xiao

Institutions: Kyoto University, Tsinghua University, University of Chinese Academy of Sciences, Chongqing Polytechnic University of Electronic Technology

Language: English

Topic: Black Holes and Theoretical Physics

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: diamond

Funders: Ministry of Education, Culture, Sports, Science and Technology, National Natural Science Foundation of China, Japan Society for the Promotion of Science, National Key Research and Development Program of China

Awards: G107065781, G2738887405, G4146574254, G5501581468, G7940611361