Updated DM-ONLY power spectrum:

Accidentally I was using Lepfrog for the particles update, now using Kick-Drift-Kick ( same as Nyx ) the max differences are 0.3%

Gas Temperature:

The initial temperature of the gas set by Nyx is \(1000 K\) at \(z=100\), I believe this is too high, previously I always used \(170 K\) for the initial temperature. Here is the mean temperature evolution for both codes, the green line is the \(a^{-2}\) dependence expected for a \(\gamma = 5/3\) gas under cosmological adiabatic expansion.

Thermal history:

Here is a plot of the thermal history for both codes, on the top of the figure you can see the redshift and the corresponding average Temperature

Hydro power spectrum:

Finally, the differences on the gas power spectrum are huge, I believe it’s because of the large differences on the temperatures.

As a reference here are the latest results from comparing to Enzo: