Einstein-Vlasov Calculations of Structure Formation. (arXiv:1908.05683v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+East_W/0/1/0/all/0/1">William E. East</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wojtak_R/0/1/0/all/0/1">Radosław Wojtak</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pretorius_F/0/1/0/all/0/1">Frans Pretorius</a>
We study the dynamics of small inhomogeneities in an expanding universe
collapsing to form bound structures using full solutions of the Einstein-Vlasov
(N-body) equations. We compare these to standard Newtonian N-body solutions
using quantities defined with respect to fiducial observers in order to bound
relativistic effects. We focus on simplified initial conditions containing a
limited range of length scales, but vary the inhomogeneities from small
magnitude, where the Newtonian and GR calculations agree quite well, to large
magnitude, where the background metric receives an order one correction. For
large inhomogeneities, we find that the collapse of overdensities tends to
happen faster in Newtonian calculations relative to fully general-relativistic
ones. Even in this extreme regime, the differences in the spacetime evolution
outside the regions of large gravitational potential and velocity are small.
For standard cosmological values, we corroborate the robustness of Newtonian
N-body simulations to model large scale perturbations and the related cosmic
variance in the local expansion rate.
We study the dynamics of small inhomogeneities in an expanding universe
collapsing to form bound structures using full solutions of the Einstein-Vlasov
(N-body) equations. We compare these to standard Newtonian N-body solutions
using quantities defined with respect to fiducial observers in order to bound
relativistic effects. We focus on simplified initial conditions containing a
limited range of length scales, but vary the inhomogeneities from small
magnitude, where the Newtonian and GR calculations agree quite well, to large
magnitude, where the background metric receives an order one correction. For
large inhomogeneities, we find that the collapse of overdensities tends to
happen faster in Newtonian calculations relative to fully general-relativistic
ones. Even in this extreme regime, the differences in the spacetime evolution
outside the regions of large gravitational potential and velocity are small.
For standard cosmological values, we corroborate the robustness of Newtonian
N-body simulations to model large scale perturbations and the related cosmic
variance in the local expansion rate.
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