We revisit techniques for performing cosmological simulations with both baryons and cold dark matter when each fluid has different initial conditions, as is the case at the end of the radiation era. Most simulations do not reproduce the linear prediction for the difference between the cold dark matter and baryon perturbations. We show that this is due to the common use of offset regular grids when setting up the particle initial conditions. The correct behaviour can be obtained without any loss of simulation resolution by using a Lagrangian glass for the baryon particles. We further show that the difference between cold dark matter and baryons may affect predictions for the Lyman-alpha forest flux power spectrum at the 5% level, potentially impacting current cosmological constraints.

中文翻译：

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使用单独的重子和暗物质初始条件进行更准确的模拟

当每种流体具有不同的初始条件时，我们重新审视使​​用重子和冷暗物质进行宇宙学模拟的技术，就像辐射时代末期的情况一样。大多数模拟不能再现冷暗物质和重子扰动之间差异的线性预测。我们表明这是由于在设置粒子初始条件时经常使用偏移规则网格。通过对重子粒子使用拉格朗日玻璃，可以在不损失模拟分辨率的情况下获得正确的行为。我们进一步表明，冷暗物质和重子之间的差异可能会影响对 Lyman-alpha 森林通量功率谱在 5% 水平上的预测，从而可能影响当前的宇宙学约束。