Non-Gaussianities from ekpyrotic collapse with multiple fields
| dc.creator | Koyama, Kazuya | |
| dc.creator | Mizuno, Shuntaro | |
| dc.creator | Vernizzi, Filippo | |
| dc.creator | Wands, David | |
| dc.date | 2007-08-31 | |
| dc.date | 2009-04-29 | |
| dc.date.accessioned | 2026-07-07T13:09:08Z | |
| dc.date.available | 2026-07-07T13:09:08Z | |
| dc.description | 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, $ϕ_1$ and $ϕ_2$, with exponential potentials, $-V_i \exp (-c_i ϕ_i)$, 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 $f_{NL} = 5 c_j^2 /12$, where $c_j$ is the exponent of the potential for the field which becomes sub-dominant 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. By combining the present observational constraints on $f_{\rm NL}$ and the scalar spectral index, the specific model studied in this paper is thus ruled out by current observational data. | |
| dc.description | 22 pages, 1figure, version revised after journal publication: sign error corrected in the value of non-linear parameter, fNL. The resulting fNL is large and negative and thus in conflict with current observational bounds | |
| dc.identifier | https://arxiv.org/abs/0708.4321 | |
| dc.identifier | http://arxiv.org/abs/0708.4321 | |
| dc.identifier | JCAP 0711:024,2007 | |
| dc.identifier | doi:10.1088/1475-7516/2007/11/024 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/228639 | |
| dc.subject | High Energy Physics - Theory | |
| dc.subject | Astrophysics | |
| dc.subject | General Relativity and Quantum Cosmology | |
| dc.title | Non-Gaussianities from ekpyrotic collapse with multiple fields | |
| dc.type | text |