# Entanglement negativity in the multiverse

## Abstract

We explore quantum entanglement between two causally disconnected regions in the multiverse. We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space. The qualitative feature of it turns out to be in agreement with that of the entanglement entropy. We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces. When one of the observers remains constrained to a region of the open chart in a de Sitter space, we find that the scale dependence enters into the entanglement. We show that a state which is initially maximally entangled becomes more entangled or less entangled on large scales depending on the mass of the scalar field and recovers the initial entanglement in the small scale limit. We argue that quantum entanglement may provide some evidence for the existence of the multiverse.

- Authors:

- Department of Theoretical Physics and History of Science, University of the Basque Country UPV/EHU, 48080 Bilbao (Spain)
- (Spain)
- (South Africa)
- Laboratory for Quantum Gravity & Strings and Astrophysics, Cosmology & Gravity Center, Department of Mathematics & Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701 (South Africa)
- Department of Physics, Kobe University, Kobe 657-8501 (Japan)

- Publication Date:

- Sponsoring Org.:
- SCOAP3, CERN, Geneva (Switzerland)

- OSTI Identifier:
- 22454521

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 03; Other Information: PUBLISHER-ID: JCAP03(2015)015; OAI: oai:repo.scoap3.org:9514; Article funded by SCOAP3. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 License. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DE SITTER SPACE; ENTROPY; QUANTUM COSMOLOGY; QUANTUM ENTANGLEMENT; QUANTUM FIELD THEORY; SCALAR FIELDS; UNIVERSE

### Citation Formats

```
Kanno, Sugumi, IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013, Bilbao, Laboratory for Quantum Gravity & Strings and Astrophysics, Cosmology & Gravity Center, Department of Mathematics & Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701, Shock, Jonathan P., National Institute for Theoretical Physics, Private Bag X1, Matieland, 7602, and Soda, Jiro.
```*Entanglement negativity in the multiverse*. United States: N. p., 2015.
Web. doi:10.1088/1475-7516/2015/03/015.

```
Kanno, Sugumi, IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013, Bilbao, Laboratory for Quantum Gravity & Strings and Astrophysics, Cosmology & Gravity Center, Department of Mathematics & Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701, Shock, Jonathan P., National Institute for Theoretical Physics, Private Bag X1, Matieland, 7602, & Soda, Jiro.
```*Entanglement negativity in the multiverse*. United States. doi:10.1088/1475-7516/2015/03/015.

```
Kanno, Sugumi, IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013, Bilbao, Laboratory for Quantum Gravity & Strings and Astrophysics, Cosmology & Gravity Center, Department of Mathematics & Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701, Shock, Jonathan P., National Institute for Theoretical Physics, Private Bag X1, Matieland, 7602, and Soda, Jiro. Tue .
"Entanglement negativity in the multiverse". United States.
doi:10.1088/1475-7516/2015/03/015.
```

```
@article{osti_22454521,
```

title = {Entanglement negativity in the multiverse},

author = {Kanno, Sugumi and IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013, Bilbao and Laboratory for Quantum Gravity & Strings and Astrophysics, Cosmology & Gravity Center, Department of Mathematics & Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7701 and Shock, Jonathan P. and National Institute for Theoretical Physics, Private Bag X1, Matieland, 7602 and Soda, Jiro},

abstractNote = {We explore quantum entanglement between two causally disconnected regions in the multiverse. We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space. The qualitative feature of it turns out to be in agreement with that of the entanglement entropy. We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces. When one of the observers remains constrained to a region of the open chart in a de Sitter space, we find that the scale dependence enters into the entanglement. We show that a state which is initially maximally entangled becomes more entangled or less entangled on large scales depending on the mass of the scalar field and recovers the initial entanglement in the small scale limit. We argue that quantum entanglement may provide some evidence for the existence of the multiverse.},

doi = {10.1088/1475-7516/2015/03/015},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 03,

volume = 2015,

place = {United States},

year = {Tue Mar 10 00:00:00 EDT 2015},

month = {Tue Mar 10 00:00:00 EDT 2015}

}