# Decoherence can relax cosmic acceleration

## Abstract

In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the system decoheres into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.

- Authors:

- Department of Physics, King’s College London,Strand, London WC2R 2LS (United Kingdom)

- Publication Date:

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

- OSTI Identifier:
- 22572184

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2016; Journal Issue: 11; Other Information: PUBLISHER-ID: JCAP11(2016)026; OAI: oai:repo.scoap3.org:17889; cc-by 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:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CONFORMAL INVARIANCE; COSMOLOGY; DE SITTER GROUP; DE SITTER SPACE; MIXED STATES; NONLUMINOUS MATTER; QUANTUM DECOHERENCE; QUANTUM FIELD THEORY; QUANTUM MECHANICS; SCALAR FIELDS; UNIVERSE; VACUUM STATES

### Citation Formats

```
Markkanen, Tommi.
```*Decoherence can relax cosmic acceleration*. United States: N. p., 2016.
Web. doi:10.1088/1475-7516/2016/11/026.

```
Markkanen, Tommi.
```*Decoherence can relax cosmic acceleration*. United States. doi:10.1088/1475-7516/2016/11/026.

```
Markkanen, Tommi. Fri .
"Decoherence can relax cosmic acceleration". United States.
doi:10.1088/1475-7516/2016/11/026.
```

```
@article{osti_22572184,
```

title = {Decoherence can relax cosmic acceleration},

author = {Markkanen, Tommi},

abstractNote = {In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the system decoheres into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.},

doi = {10.1088/1475-7516/2016/11/026},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 11,

volume = 2016,

place = {United States},

year = {Fri Nov 11 00:00:00 EST 2016},

month = {Fri Nov 11 00:00:00 EST 2016}

}

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