Implementing the DC Mode in Cosmological Simulations with Supercomoving   Variables
  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. 
Nickolay Y. Gnedin, Andrey V. Kravtsov, and Douglas H. Rudd
astro-ph.CO