**Authors**: Nora Elisa Chisari, Matias Zaldarriaga

**Date**: 18 Jan 2011

**Abstract**: On large scales, comparable to the horizon, the observable clustering properties of galaxies are affected by various General Relativistic effects. To calculate these effects one needs to consistently solve for the metric, densities and velocities in a specific coordinate system or gauge. The method of choice for simulating large scale structure is numerical N-body simulations which are performed in the Newtonian limit. Even though one might worry that the use of the Newtonian approximation would make it impossible to use these simulations to compute properties on very large scales we show that the simulations are still solving the dynamics correctly even for long modes and give formulas to obtain the position of particles in the Newtonian gauge given the positions computed in the simulation. We also give formulas to convert from the output coordinates of N-body simulations to the observable coordinates of the particles.

1101.3555
(/preprints)

2011-01-20, 09:18
**[edit]**

© M. Vallisneri 2012 — last modified on 2010/01/29

*Tantum in modicis, quantum in maximis*