A parallel world in the dark

Tetsutaro Higaki, Kwang Sik Jeong, Fuminobu Takahashi

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


The baryon-dark matter coincidence is a long-standing issue. Interestingly, the recent observations suggest the presence of dark radiation, which, if confirmed, would pose another coincidence problem of why the density of dark radiation is comparable to that of photons. These striking coincidences may be traced back to the dark sector with particle contents and interactions that are quite similar, if not identical, to the standard model: a dark parallel world. It naturally solves the coincidence problems of dark matter and dark radiation, and predicts a sterile neutrino(s) with mass of (0.1-1) eV, as well as self-interacting dark matter made of the counterpart of ordinary baryons. We find a robust prediction for the relation between the abundance of dark radiation and the sterile neutrino, which can serve as the smoking-gun evidence of the dark parallel world.

Original languageEnglish
Article number031
JournalJournal of Cosmology and Astroparticle Physics
Issue number8
Publication statusPublished - 2013 Aug


  • cosmological neutrinos
  • dark matter theory
  • string theory and cosmology


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