Inflation model selection meets dark radiation

Thomas Tram, Robert Vallance, Vincent Vennin

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Abstract

We investigate how inflation model selection is affected by the presence of additional free-streaming relativistic degrees of freedom, i.e. dark radiation. We perform a full Bayesian analysis of both inflation parameters and cosmological parameters taking reheating into account self-consistently. We compute the Bayesian evidence for a few representative inflation scenarios in both the standard ΛCDM model and an extension including dark radiation parametrised by its effective number of relativistic species Neff. Using a minimal dataset (Planck low-ℓ polarisation, temperature power spectrum and lensing reconstruction), we find that the observational status of most inflationary models is unchanged. The exceptions are potentials such as power-law inflation that predict large values for the scalar spectral index that can only be realised when Neff is allowed to vary. Adding baryon acoustic oscillations data and the B-mode data from BICEP2/Keck makes power-law inflation disfavoured, while adding local measurements of the Hubble constant H0 makes power-law inflation slightly favoured compared to the best single-field plateau potentials. This illustrates how the dark radiation solution to the H0 tension would have deep consequences for inflation model selection.
Original languageEnglish
JournalJournal of Cosmology and Astroparticle Physics
Volume1701 (2017)
Issue number01, 046
DOIs
Publication statusPublished - 23 Jan 2017

Keywords

  • inflation
  • cosmological neutrinos
  • RCUK
  • STFC
  • ST/K00090X/1
  • ST/N000668/1

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