Concordance cosmology without dark energy

Gábor Rácz, László Dobos, Róbert Beck, István Szapudi, István Csabai

Research output: Contribution to journalArticle

23 Citations (Scopus)


According to the separate universe conjecture, spherically symmetric sub-regions in an isotropic universe behave like mini-universes with their own cosmological parameters. This is an excellent approximation in both Newtonian and general relativistic theories. We estimate local expansion rates for a large number of such regions, and use a scale parameter calculated from the volume-averaged increments of local scale parameters at each time step in an otherwise standard cosmological N-body simulation. The particle mass, corresponding to a coarse graining scale, is an adjustable parameter. This mean field approximation neglects tidal forces and boundary effects, but it is the first step towards a non-perturbative statistical estimation of the effect of non-linear evolution of structure on the expansion rate. Using our algorithm, a simulation with an initial Ωm = 1 Einstein–de Sitter setting closely tracks the expansion and structure growth history of the ∧ cold dark matter (∧CDM) cosmology. Due to small but characteristic differences, our model can be distinguished from the ∧CDM model by future precision observations. Moreover, our model can resolve the emerging tension between local Hubble constant measurements and the Planck best-fitting cosmology. Further improvements to the simulation are necessary to investigate light propagation and confirm full consistency with cosmic microwave background observations.

Original languageEnglish
Pages (from-to)L1-L5
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Publication statusPublished - Jul 2017


  • Cosmological parameters
  • Dark energy
  • Methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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