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%
The initial temperature of the gas set by Nyx is at , I believe this is too high, previously I always used for the initial temperature. Here is the mean temperature evolution for both codes, the green line is the dependence expected for a gas under cosmological adiabatic expansion.
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: