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Reduced density matrix and internal dynamics for multicomponent regions

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arxiv 0903.5284 v3 pith:6YCKTZ26 submitted 2009-03-30 hep-th

classification hep-th
keywords densitymatrixcasedisjointflowinternalintervalintervals
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We find the density matrix corresponding to the vacuum state of a massless Dirac field in two dimensions reduced to a region of the space formed by several disjoint intervals. We calculate explicitly its spectral decomposition. The imaginary powers of the density matrix is a unitary operator implementing an internal time flow (the modular flow). We show that in the case of more than one interval this evolution is non-local, producing both, advance in the causal structure and "teleportation" between the disjoint intervals. However, it only mixes the fields on a finite number of trajectories, one for each interval. As an application of these results we compute the entanglement entropy for the massive multi-interval case in the small mass limit.

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Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Uniqueness of null-local modular flow

    hep-th 2026-07 conditional novelty 7.0 of 10

    For the free massless scalar in a Minkowski causal diamond, the vacuum is the unique state or weight in the vacuum sector whose modular flow is local on the null boundary.

  2. Modular Hamiltonian and entanglement entropy in the BMS free fermion theory

    hep-th 2025-07 conditional novelty 6.0 of 10

    In the BMS free fermion model, the two-interval modular Hamiltonian has local plus bi-local terms, and the vacuum entanglement entropy for n intervals is the chiral-CFT formula with c_L=1 and c_M=0.

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