NonGaussianity from selfordering scalar fields
Abstract
The Universe may harbor relics of the postinflationary epoch in the form of a network of selfordered scalar fields. Such fossils, while consistent with current cosmological data at trace levels, may leave too weak an imprint on the cosmic microwave background and the largescale distribution of matter to allow for direct detection. The nonGaussian statistics of the density perturbations induced by these fields, however, permit a direct means to probe for these relics. Here we calculate the bispectrum that arises in models of selfordered scalar fields. We find a compact analytic expression for the bispectrum, evaluate it numerically, and provide a simple approximation that may be useful for data analysis. The bispectrum is largest for triangles that are aligned (have edges k_{1}≃2k_{2}≃2k_{3}) as opposed to the localmodel bispectrum, which peaks for squeezed triangles (k_{1}≃k_{2}≫k_{3}), and the equilateral bispectrum, which peaks at k_{1}≃k_{2}≃k_{3}. We estimate that this nonGaussianity should be detectable by the Planck satellite if the contribution from selfordering scalar fields to primordial perturbations is near the current upper limit.
 Publication:

Physical Review D
 Pub Date:
 June 2010
 DOI:
 10.1103/PhysRevD.81.123504
 arXiv:
 arXiv:1003.0672
 Bibcode:
 2010PhRvD..81l3504F
 Keywords:

 98.80.k;
 11.30.Fs;
 98.80.Cq;
 Cosmology;
 Global symmetries;
 Particletheory and fieldtheory models of the early Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology
 EPrint:
 11 pages, 1 figure