Small field models with gravitational wave signature supported by CMB data

Ira Wolfson, Ramy Brustein

Research output: Contribution to journalArticlepeer-review


We study scale dependence of the cosmic microwave background (CMB) power spectrum in a class of small, single-field models of inflation which lead to a high value of the tensor to scalar ratio. The inflaton potentials that we consider are degree 5 polynomials, for which we precisely calculate the power spectrum, and extract the cosmological parameters: the scalar index ns, the running of the scalar index nrun and the tensor to scalar ratio r. We find that for non-vanishing nrun and for r as small as r = 0.001, the precisely calculated values of ns and nrun deviate significantly from what the standard analytic treatment predicts. We study in detail, and discuss the probable reasons for such deviations. As such, all previously considered models (of this kind) are based upon inaccurate assumptions. We scan the possible values of potential parameters for which the cosmological parameters are within the allowed range by observations. The 5 parameter class is able to reproduce all of the allowed values of ns and nrun for values of r that are as high as 0.001. Subsequently this study at once refutes previous such models built using the analytical Stewart-Lyth term, and revives the small field brand, by building models that do yield an appreciable r while conforming to known CMB observables.

Original languageAmerican English
Article numbere0197735
JournalPLoS ONE
Issue number5
StatePublished - 1 May 2018

All Science Journal Classification (ASJC) codes

  • General
  • General Biochemistry,Genetics and Molecular Biology
  • General Agricultural and Biological Sciences


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