Abstract
We compute the non-Gaussianity of the curvature perturbation generated by ekpyrotic collapse with multiple fields. The transition from the multi-field scaling solution to a single-field dominated regime converts initial isocurvature field perturbations to an almost scale invariant comoving curvature perturbation. In the specific model of two fields, 1 and 2, with exponential potentials, -Viexp(-ci i), we calculate the bispectrum of the resulting curvature perturbation. We find that the non-Gaussianity is dominated by non-linear evolution on super-Hubble scales and hence is of the local form. The non-linear parameter of the curvature perturbation is given by fNL = 5c j 2/12, where cj is the exponent of the potential for the field which becomes subdominant at late times. Since c j 2 must be large, in order to generate an almost scale invariant spectrum, the non-Gaussianity is inevitably large. Thus, the model is strongly constrained by observational bounds on the spectral index and non-Gaussianity.
| Original language | English |
|---|---|
| Article number | 024 |
| Journal | Journal of Cosmology and Astroparticle Physics |
| Issue number | 11 |
| DOIs | |
| Publication status | Published - 2007 Nov 1 |
| Externally published | Yes |
Fingerprint
Keywords
- Cosmological perturbation theory
- Cosmology with extra dimensions
- String theory and cosmology
ASJC Scopus subject areas
- Physics and Astronomy(all)
Cite this
Non-Gaussianities from ekpyrotic collapse with multiple fields. / Koyama, Kazuya; Mizuno, Shuntaro; Vernizzi, Filippo; Wands, David.
In: Journal of Cosmology and Astroparticle Physics, No. 11, 024, 01.11.2007.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Non-Gaussianities from ekpyrotic collapse with multiple fields
AU - Koyama, Kazuya
AU - Mizuno, Shuntaro
AU - Vernizzi, Filippo
AU - Wands, David
PY - 2007/11/1
Y1 - 2007/11/1
N2 - We compute the non-Gaussianity of the curvature perturbation generated by ekpyrotic collapse with multiple fields. The transition from the multi-field scaling solution to a single-field dominated regime converts initial isocurvature field perturbations to an almost scale invariant comoving curvature perturbation. In the specific model of two fields, 1 and 2, with exponential potentials, -Viexp(-ci i), we calculate the bispectrum of the resulting curvature perturbation. We find that the non-Gaussianity is dominated by non-linear evolution on super-Hubble scales and hence is of the local form. The non-linear parameter of the curvature perturbation is given by fNL = 5c j 2/12, where cj is the exponent of the potential for the field which becomes subdominant at late times. Since c j 2 must be large, in order to generate an almost scale invariant spectrum, the non-Gaussianity is inevitably large. Thus, the model is strongly constrained by observational bounds on the spectral index and non-Gaussianity.
AB - We compute the non-Gaussianity of the curvature perturbation generated by ekpyrotic collapse with multiple fields. The transition from the multi-field scaling solution to a single-field dominated regime converts initial isocurvature field perturbations to an almost scale invariant comoving curvature perturbation. In the specific model of two fields, 1 and 2, with exponential potentials, -Viexp(-ci i), we calculate the bispectrum of the resulting curvature perturbation. We find that the non-Gaussianity is dominated by non-linear evolution on super-Hubble scales and hence is of the local form. The non-linear parameter of the curvature perturbation is given by fNL = 5c j 2/12, where cj is the exponent of the potential for the field which becomes subdominant at late times. Since c j 2 must be large, in order to generate an almost scale invariant spectrum, the non-Gaussianity is inevitably large. Thus, the model is strongly constrained by observational bounds on the spectral index and non-Gaussianity.
KW - Cosmological perturbation theory
KW - Cosmology with extra dimensions
KW - String theory and cosmology
UR - http://www.scopus.com/inward/record.url?scp=36749091266&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=36749091266&partnerID=8YFLogxK
U2 - 10.1088/1475-7516/2007/11/024
DO - 10.1088/1475-7516/2007/11/024
M3 - Article
AN - SCOPUS:36749091266
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
IS - 11
M1 - 024
ER -