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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

Reduced density matrix and internal dynamics for multicomponent regions

classification hep-th
keywords densitymatrixcasedisjointflowinternalintervalintervals
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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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 3 Pith papers

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

  1. Mutual Information from Modular Flow in General CFTs

    hep-th 2026-04 unverdicted novelty 8.0

    A hierarchy of approximations to the mutual information in CFTs is derived from modular flow and two-point functions of primaries, providing a high-precision formula for arbitrary ball separations that supersedes prev...

  2. Uniqueness of null-local modular flow

    hep-th 2026-07 conditional novelty 7.0

    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.

  3. Local Strong-to-Weak Spontaneous Symmetry Breaking

    quant-ph 2026-05 unverdicted novelty 7.0

    Introduces a local one-point fidelity correlator to define SW-SSB, preserving key features like channel stability and long-range conditional mutual information while enabling detection in large and thermodynamic-limit...