Newtonian kinematical backreaction in cosmological $N$-body simulations with Delaunay Tesselation: "zero test" and scale dependence

TL;DR

This paper assesses the impact of inhomogeneities on the universe's large-scale properties using N-body simulations and Delaunay Tessellation, focusing on the kinematical backreaction and its scale dependence to improve relativistic cosmological models.

Contribution

It introduces a method to measure kinematical backreaction in N-body simulations using DTFE and explores its scale dependence, advancing towards relativistic inhomogeneous simulations.

Findings

DTFE effectively estimates kinematical backreaction Q.

Q shows statistical dependence on length scale.

Comparison of interpolation techniques highlights their impact on Q.

Abstract

The backreaction of inhomogeneities describes the effect of inhomogeneous structure on average properties of the Universe. We investigate this approach by testing the consistency of cosmological $N$-body simulations as non-linear structure evolves. Using the Delaunay Tessellation Field Estimator (DTFE), we calculate the kinematical backreaction $Q$ from simulations on different scales in order to measure how much $N$-body simulations should be corrected for this effect. This is the first step towards creating fully relativistic and inhomogeneous $N$-body simulations. In this paper we compare the interpolation techniques available in DTFE and illustrate the statistical dependence of $Q$ as a function of length scale.