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arXiv · 1805.10651

Gluing together Modular flows with free fermions

Gabriel Wong
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Abstract

We revisit the calculation of multi-interval modular Hamiltonians for free fermions using a Euclidean path integral approach. We show how the multi-interval modular flow is obtained by gluing together the single interval modular flows. Using this relation, we obtain an exact expression for the multi-interval modular Hamiltonian and entanglement entropy in agreement with existing results. An essential ingredient in our derivation is the introduction of the \emp{modular action}. This determines the non-local field theory describing the free fermion reduced density matrix, and makes manifest it's non-local conformal symmetry and $U(1)$ Kacs-Moody symmetry.

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Gabriel Wong. 2019-02-15. Gluing together Modular flows with free fermions. https://doi.org/10.1007/jhep04(2019)045

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