Implementing the DC Mode in Cosmological Simulations with Supercomoving Variables

TL;DR

This paper demonstrates how to incorporate the DC mode into cosmological simulations using supercomoving variables, improving the accuracy of modeling spatial correlations and halo abundance in small simulation boxes.

Contribution

It provides a straightforward method to include the DC mode in cosmological codes utilizing supercomoving variables, simplifying the equations governing dark matter and baryon evolution.

Findings

Inclusion of the DC mode affects halo abundance in small boxes.

The supercomoving variable formulation simplifies the equations of motion.

Explicit incorporation of the DC mode improves simulation accuracy.

Abstract

As emphasized by previous studies, proper treatment of the density fluctuation on the fundamental scale of a cosmological simulation volume - the "DC mode" - is critical for accurate modeling of spatial correlations on scales > 10% of simulation box size. We provide further illustration of the effects of the DC mode on the abundance of halos in small boxes and show that it is straightforward to incorporate this mode in cosmological codes that use the "supercomoving" variables. The equations governing evolution of dark matter and baryons recast with these variables are particularly simple and include the expansion factor, and hence the effect of the DC mode, explicitly only in the Poisson equation.