### 摘要

In cosmological scenarios such as the pre-big bang scenario or the ekpyrotic scenario, a matching condition between the metric perturbations in the pre-big bang phase and those in the post big bang phase is often assumed. Various matching conditions have been considered in the literature. Nevertheless obtaining a scale-invariant CMB spectrum via a concrete mechanism remains impossible. In this paper, we examine this problem from the point of view of local causality. We begin with introducing the notion of local causality and explain how it constrains the form of the matching condition. We then prove a no-go theorem: independent of the details of the matching condition, a scale-invariant spectrum is impossible as long as the local causality condition is satisfied. In our framework, it is easy to show that a violation of local causality around the bounce is needed in order to give a scale-invariant spectrum. We study a specific scenario of this possibility by considering a nonlocal effective theory inspired by noncommutative geometry around the bounce and show that a scale-invariant spectrum is possible. Moreover we demonstrate that the magnitude of the spectrum is compatible with observations if the bounce is assumed to occur at an energy scale which is a few orders of magnitude below the Planckian energy scale.

原文 | 英語 |
---|---|

文章編號 | 103505 |

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

卷 | 73 |

發行號 | 10 |

DOIs | |

出版狀態 | 已發佈 - 2006 五月 18 |

### 指紋

### ASJC Scopus subject areas

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

### 引用此文

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

*73*(10), [103505]. https://doi.org/10.1103/PhysRevD.73.103505

**Nonlocal matching condition and scale-invariant spectrum in bouncing cosmology.** / Chu, Chong Sun; Furuta, Ko; Lin, Feng Li.

研究成果: 雜誌貢獻 › 文章

*Physical Review D - Particles, Fields, Gravitation and Cosmology*, 卷 73, 編號 10, 103505. https://doi.org/10.1103/PhysRevD.73.103505

}

TY - JOUR

T1 - Nonlocal matching condition and scale-invariant spectrum in bouncing cosmology

AU - Chu, Chong Sun

AU - Furuta, Ko

AU - Lin, Feng Li

PY - 2006/5/18

Y1 - 2006/5/18

N2 - In cosmological scenarios such as the pre-big bang scenario or the ekpyrotic scenario, a matching condition between the metric perturbations in the pre-big bang phase and those in the post big bang phase is often assumed. Various matching conditions have been considered in the literature. Nevertheless obtaining a scale-invariant CMB spectrum via a concrete mechanism remains impossible. In this paper, we examine this problem from the point of view of local causality. We begin with introducing the notion of local causality and explain how it constrains the form of the matching condition. We then prove a no-go theorem: independent of the details of the matching condition, a scale-invariant spectrum is impossible as long as the local causality condition is satisfied. In our framework, it is easy to show that a violation of local causality around the bounce is needed in order to give a scale-invariant spectrum. We study a specific scenario of this possibility by considering a nonlocal effective theory inspired by noncommutative geometry around the bounce and show that a scale-invariant spectrum is possible. Moreover we demonstrate that the magnitude of the spectrum is compatible with observations if the bounce is assumed to occur at an energy scale which is a few orders of magnitude below the Planckian energy scale.

AB - In cosmological scenarios such as the pre-big bang scenario or the ekpyrotic scenario, a matching condition between the metric perturbations in the pre-big bang phase and those in the post big bang phase is often assumed. Various matching conditions have been considered in the literature. Nevertheless obtaining a scale-invariant CMB spectrum via a concrete mechanism remains impossible. In this paper, we examine this problem from the point of view of local causality. We begin with introducing the notion of local causality and explain how it constrains the form of the matching condition. We then prove a no-go theorem: independent of the details of the matching condition, a scale-invariant spectrum is impossible as long as the local causality condition is satisfied. In our framework, it is easy to show that a violation of local causality around the bounce is needed in order to give a scale-invariant spectrum. We study a specific scenario of this possibility by considering a nonlocal effective theory inspired by noncommutative geometry around the bounce and show that a scale-invariant spectrum is possible. Moreover we demonstrate that the magnitude of the spectrum is compatible with observations if the bounce is assumed to occur at an energy scale which is a few orders of magnitude below the Planckian energy scale.

UR - http://www.scopus.com/inward/record.url?scp=33646520572&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33646520572&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.73.103505

DO - 10.1103/PhysRevD.73.103505

M3 - Article

AN - SCOPUS:33646520572

VL - 73

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

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

SN - 1550-7998

IS - 10

M1 - 103505

ER -