Dark radiation from modulated reheating

Takeshi Kobayashi, Fuminobu Takahashi, Tomo Takahashi, Masahide Yamaguchi

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


We show that the modulated reheating mechanism can naturally account for dark radiation, whose existence is hinted by recent observations of the cosmic microwave background radiation and the primordial Helium abundance. In this mechanism, the inflaton decay rate depends on a light modulus which acquires almost scale-invariant quantum fluctuations during inflation. We find that the light modulus is generically produced by the inflaton decay and therefore a prime candidate for the dark radiation. Interestingly, an almost scale-invariant power spectrum predicted in the modulated reheating mechanism gives a better fit to the observation in the presence of the extra radiation. We discuss the production mechanism of the light modulus in detail taking account of its associated isocurvature fluctuations. We also consider a case where the modulus becomes the dominant component of dark matter.

Original languageEnglish
Article number036
JournalJournal of Cosmology and Astroparticle Physics
Issue number3
Publication statusPublished - 2012 Mar


  • cosmology of theories beyond the SM
  • dark matter theory
  • inflation
  • physics of the early universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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