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Title: General mechanism for producing scale-invariant perturbations and small non-Gaussianity in ekpyrotic models

Journal Article · · Physical Review. D, Particles, Fields, Gravitation and Cosmology
 [1];  [2];  [3]
  1. Max-Planck-Inst. for Gravitational Physics, Potsdam (Germany); Rutgers Univ., New Brunswick, NJ (United States)
  2. Max-Planck-Inst. for Gravitational Physics, Potsdam (Germany)
  3. Princeton Univ., NJ (United States)
+ Show Author Affiliations

We explore a new type of entropic mechanism for generating density perturbations in a contracting phase in which there are two scalar fields, but only one has a steep negative potential. This first field dominates the energy density and is the source of the ekpyrotic equation of state. The second field has a negligible potential, but its kinetic energy density is coupled to the first field with a non-linear sigma-model type interaction. We show that for any ekpyrotic equation of state it is possible to choose the potential and the kinetic coupling such that exactly scale-invariant (or nearly scale-invariant) entropy perturbations are produced. The corresponding background solutions are stable, and the bispectrum of the entropy perturbations vanishes as no non-Gaussianity is produced during the ekpyrotic phase. Finally, the only contribution to non-Gaussianity comes from the non-linearity of the conversion process during which entropic perturbations are turned into adiabatic ones, resulting in a local non-Gaussianity parameter fNL~5.

Research Organization:
Princeton Univ., NJ (United States)
Sponsoring Organization:
USDOE Office of Science (SC), High Energy Physics (HEP); European Research Council (ERC)
Grant/Contract Number:
SC0007968; FG02-91ER40671; 256994
OSTI ID:
1600652
Journal Information:
Physical Review. D, Particles, Fields, Gravitation and Cosmology, Vol. 89, Issue 12; ISSN 1550-7998
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 41 works
Citation information provided by
Web of Science

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Cited By (16)

Matter bounce cosmology with a generalized single field: non-Gaussianity and an extended no-go theorem journal March 2017
Theoretical cosmology journal November 2019
Bouncing cosmology made simple journal June 2018
Implications of Planck2015 for inflationary, ekpyrotic and anamorphic bouncing cosmologies journal January 2016
Converting entropy to curvature perturbations after a cosmic bounce journal October 2016
Cosmology and Fundamental Physics with the Euclid Satellite journal September 2013
Nonsingular bouncing cosmology: Consistency of the effective description journal May 2016
Bouncing Cosmologies: Progress and Problems journal February 2017
Cosmology and fundamental physics with the Euclid satellite journal April 2018
Cosmology and fundamental physics with the Euclid satellite text January 2018
Cosmology and fundamental physics with the Euclid satellite text January 2012
Scale-invariant perturbations in ekpyrotic cosmologies without fine-tuning of initial conditions text January 2015
Implications of Planck2015 for inflationary, ekpyrotic and anamorphic bouncing cosmologies text January 2015
Bouncing Cosmologies: Progress and Problems text January 2016
Matter bounce cosmology with a generalized single field: non-Gaussianity and an extended no-go theorem text January 2016
Theoretical Cosmology text January 2019

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Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS