Relativistic initial conditions for N-body simulations
Initial conditions for (Newtonian) cosmological N-body simulations are usually set by re-scaling the present-day power spectrum obtained from linear (relativistic) Boltzmann codes to the desired initial redshift of the simulation. This back-scaling method can account for the effect of inhomogeneous...
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| Main Authors: | , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
22 June 2017
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| In: |
Journal of cosmology and astroparticle physics
Year: 2017, Issue: 6, Pages: 1-20 |
| ISSN: | 1475-7516 |
| DOI: | 10.1088/1475-7516/2017/06/043 |
| Online Access: | Verlag, Volltext: http://dx.doi.org/10.1088/1475-7516/2017/06/043 Verlag, Volltext: http://stacks.iop.org/1475-7516/2017/i=06/a=043 
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| Author Notes: | Christian Fidler, Thomas Tram, Cornelius Rampf, Robert Crittenden, Kazuya Koyama and David Wands |
| Summary: | Initial conditions for (Newtonian) cosmological N-body simulations are usually set by re-scaling the present-day power spectrum obtained from linear (relativistic) Boltzmann codes to the desired initial redshift of the simulation. This back-scaling method can account for the effect of inhomogeneous residual thermal radiation at early times, which is absent in the Newtonian simulations. We analyse this procedure from a fully relativistic perspective, employing the recently-proposed Newtonian motion gauge framework. We find that N-body simulations for ΛCDM cosmology starting from back-scaled initial conditions can be self-consistently embedded in a relativistic space-time with first-order metric potentials calculated using a linear Boltzmann code. This space-time coincides with a simple “N-body gauge” for z < 50 for all observable modes. Care must be taken, however, when simulating non-standard cosmologies. As an example, we analyse the back-scaling method in a cosmology with decaying dark matter, and show that metric perturbations become large at early times in the back-scaling approach, indicating a breakdown of the perturbative description. We suggest a suitable “forwards approach" for such cases. |
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| Item Description: | Gesehen am 29.08.2019 |
| Physical Description: | Online Resource |
| ISSN: | 1475-7516 |
| DOI: | 10.1088/1475-7516/2017/06/043 |