{
  "id": "1406.4119",
  "version": "v2",
  "published": "2014-06-16T19:58:17.000Z",
  "updated": "2015-01-13T12:47:02.000Z",
  "title": "Non-Gaussianity excess problem in classical bouncing cosmologies",
  "authors": [
    "Xian Gao",
    "Marc Lilley",
    "Patrick Peter"
  ],
  "comment": "7 pages, 2 figures. Inclusion of additional results (equations and plots) and more detailed discussion in the introduction and main body. Accepted for publication in Physical Review D",
  "categories": [
    "gr-qc",
    "astro-ph.CO",
    "hep-th"
  ],
  "abstract": "The simplest possible classical model leading to a cosmological bounce is examined in the light of the non-Gaussianities it can generate. Concentrating solely on the transition between contraction and expansion, and assuming initially purely Gaussian perturbations at the end of the contracting phase, we find that the bounce acts as a source such that the resulting value for the post-bounce $f_{\\mathrm{NL}}$ may largely exceed all current limits, to the point of potentially casting doubts on the validity of the perturbative expansion. We conjecture that if one can assume that the non-Gaussianity production depends only on the bouncing behavior of the scale factor and not on the specifics of the model examined, then many realistic models in which a nonsingular classical bounce takes place could exhibit a generic non-Gaussianity excess problem that would need to be addressed for each case.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2014-06-16T19:58:17.000Z",
      "title": "The non-Gaussianity excess problem in bouncing cosmologies",
      "abstract": "The simplest possible classical model leading to a cosmological bounce is examined in the light of the non-Gaussianities it can generate. Concentrating on the transition between contraction and expansion only, i.e. assuming initially purely Gaussian perturbations, we find that the bounce acts as a source such that the resulting value for the post-bounce $f_{\\mathrm{NL}}$ largely exceeds all current limits, and potentially casts doubt on the validity of the perturbative expansion. We conjecture that if one can assume that the non-Gaussianity production depends only on the bouncing behavior of the scale factor and not on the specifics of the model examined, then any realistic model in which a non-singular classical bounce takes place could exhibit a generic non-Gaussianity excess problem.",
      "comment": "4 pages, 3 figures",
      "journal": null,
      "doi": null
    },
    {
      "version": "v2",
      "updated": "2015-01-13T12:47:02.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "98.70.Vc",
      "98.80.Cq"
    ],
    "keywords": [
      "bouncing cosmologies",
      "generic non-gaussianity excess problem",
      "non-gaussianity production depends",
      "realistic model",
      "assuming initially purely gaussian perturbations"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1103/PhysRevD.91.023516",
      "journal": "Physical Review D",
      "year": 2015,
      "month": "Jan",
      "volume": 91,
      "number": 2,
      "pages": "023516"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 7,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1300628,
      "adsabs": "2015PhRvD..91b3516G"
    }
  }
}