Cosmological N-body simulations including radiation perturbations

Jacob Brandbyge, Cornelius Rampf, Thomas Tram, Florent Leclercq, Christian Fidler, Steen Hannestad

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Cosmological N-body simulations are the standard tools to study the emergence of the observed large-scale structure of the Universe. Such simulations usually solve for the gravitational dynamics of matter within the Newtonian approximation, thus discarding general relativistic effects such as the coupling between matter and radiation (≡ photons and neutrinos). In this Letter, we investigate novel hybrid simulations that incorporate interactions between radiation and matter to the leading order in General Relativity, whilst evolving the matter dynamics in full non-linearity according to Newtonian theory. Our hybrid simulations come with a relativistic space–time and make it possible to investigate structure formation in a unified framework. In this work, we focus on simulations initialized at z = 99 and show that the extracted matter power spectrum receives up to 3 per cent corrections on very large scales through radiation. Our numerical findings compare favourably with linear analytical results from Fidler et al., from which we deduce that there cannot be any significant non-linear mode-coupling induced through linear radiation corrections.
Original languageEnglish
Pages (from-to)L68-L72
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Early online date22 Nov 2016
Publication statusPublished - Mar 2017


  • astro-ph.CO
  • gr-qc
  • cosmology: theory
  • dark matter
  • large-scale structure of Universe


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