### Abstract

It is well known that quantum effects can produce negative energy densities, though for limited times. Here we show in the context of two-dimensional conformal field theory that such negative energy densities are present in any nontrivial conformal vacuum and can be interpreted in terms of the entanglement structure of such states. We derive an exact identity relating the outgoing energy flux and the entanglement entropy in the in-vacuum. When applied to two-dimensional models of black hole evaporation, this identity implies that unitarity is incompatible with monotonic mass loss.

Original language | English (US) |
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Article number | 041904 |

Journal | Physical Review D - Particles, Fields, Gravitation and Cosmology |

Volume | 90 |

Issue number | 4 |

DOIs | |

State | Published - Aug 27 2014 |

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### All Science Journal Classification (ASJC) codes

- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)

### Cite this

*Physical Review D - Particles, Fields, Gravitation and Cosmology*,

*90*(4), [041904]. https://doi.org/10.1103/PhysRevD.90.041904

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*Physical Review D - Particles, Fields, Gravitation and Cosmology*, vol. 90, no. 4, 041904. https://doi.org/10.1103/PhysRevD.90.041904

**Entanglement entropy and negative energy in two dimensions.** / Bianchi, Eugenio; Smerlak, Matteo.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Entanglement entropy and negative energy in two dimensions

AU - Bianchi, Eugenio

AU - Smerlak, Matteo

PY - 2014/8/27

Y1 - 2014/8/27

N2 - It is well known that quantum effects can produce negative energy densities, though for limited times. Here we show in the context of two-dimensional conformal field theory that such negative energy densities are present in any nontrivial conformal vacuum and can be interpreted in terms of the entanglement structure of such states. We derive an exact identity relating the outgoing energy flux and the entanglement entropy in the in-vacuum. When applied to two-dimensional models of black hole evaporation, this identity implies that unitarity is incompatible with monotonic mass loss.

AB - It is well known that quantum effects can produce negative energy densities, though for limited times. Here we show in the context of two-dimensional conformal field theory that such negative energy densities are present in any nontrivial conformal vacuum and can be interpreted in terms of the entanglement structure of such states. We derive an exact identity relating the outgoing energy flux and the entanglement entropy in the in-vacuum. When applied to two-dimensional models of black hole evaporation, this identity implies that unitarity is incompatible with monotonic mass loss.

UR - http://www.scopus.com/inward/record.url?scp=84934346352&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84934346352&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.90.041904

DO - 10.1103/PhysRevD.90.041904

M3 - Article

AN - SCOPUS:84934346352

VL - 90

JO - Physical Review D

JF - Physical Review D

SN - 0556-2821

IS - 4

M1 - 041904

ER -