The Galaxy number density is a key quantity to compare theoretical predictions to the observational data from current and future large scale structure surveys. The precision demanded by these stage IV surveys requires the use of second order cosmological perturbation theory. Based on the independent calculation published previously, we present the result of the comparison with the results of three other groups at leading order. Overall we find that the differences between the different approaches lie mostly on the definition of certain quantities, where the ambiguity of signs results in the addition of extra terms at second order in perturbation theory.

中文翻译：

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扰动理论中的星系数量在二阶计数：前导项比较

星系数密度是将理论预测与当前和未来大规模结构调查的观测数据进行比较的关键量。这些第四阶段调查所要求的精度需要使用二阶宇宙学扰动理论。基于之前发表的独立计算，我们以领先的顺序呈现与其他三个组的结果的比较结果。总的来说，我们发现不同方法之间的差异主要在于某些数量的定义，其中符号的歧义导致在扰动理论中添加了二阶额外项。