Matter bounce cosmology with a generalized single field: non-Gaussianity and an extended no-go theorem

Dec 6, 2016
23 pages
Published in:
  • JCAP 03 (2017) 031
  • Published: Mar 14, 2017
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Abstract: (IOP)
We extend the matter bounce scenario to a more general theory in which the background dynamics and cosmological perturbations are generated by a k-essence scalar field with an arbitrary sound speed. When the sound speed is small, the curvature perturbation is enhanced, and the tensor-to-scalar ratio, which is excessively large in the original model, can be sufficiently suppressed to be consistent with observational bounds. Then, we study the primordial three-point correlation function generated during the matter-dominated contraction stage and find that it only depends on the sound speed parameter. Similar to the canonical case, the shape of the bispectrum is mainly dominated by a local form, though for some specific sound speed values a new shape emerges and the scaling behaviour changes. Meanwhile, a small sound speed also results in a large amplitude of non-Gaussianities, which is disfavored by current observations. As a result, it does not seem possible to suppress the tensor-to-scalar ratio without amplifying the production of non-Gaussianities beyond current observational constraints (and vice versa). This suggests an extension of the previously conjectured no-go theorem in single field nonsingular matter bounce cosmologies, which rules out a large class of models. However, the non-Gaussianity results remain as a distinguishable signature of matter bounce cosmology and have the potential to be detected by observations in the near future.
Note:
  • 23 pages, 1 figure; v2: references added; v3: minor changes, minor typos corrected, references added, matches published version
  • cosmological model: bounce
  • non-Gaussianity
  • k-essence
  • curvature: perturbation
  • n-point function: 3
  • bispectrum
  • suppression
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