【Note】Tommi Markkanen, Arttu Rajantie, Stephen Stopyra, Cosmological Aspects of Higgs Vacuum Metastability, arXiv: 1809.06923
As we known, the classical potential of a field after quantization receives quantum corrections and thus becomes the effective potential
其中 即所谓重整化能标，跑动耦合参数 对重整化能标的依赖由各自的贝塔函数 给出，量子场的重整化一点函数与裸场的关系 则由场重整化因子 给出，而场重整化因子则由反常量纲 给出。
where is the so-called renormalization scale, and the dependences of running coupling parameters on the renormalization scale are given by the corresponding beta function , and the renormalized one-point function of a quantized field is related to the bare field by the field-renormalization-factor determined by the anomalous dimension .
包含所有阶圈图量子修正 的完整的有效势，其本身并不依赖于重整化能标的选取，即所谓 Callan-Symazik 方程
The full effective potential including all orders of loop-diagram quantum-corrections does not depend on the choice of renormalization scale, leading to so-called Callan-Symazik equation
如果存在重整化能标的某种选取函数 ，使得总的量子修正 为零， 那么我们就得到了一个经过重整化群提升的有效势
If there is such a choice of function for the renormalization scale so that the total quantum correction is vanished, then we have a renormalization-group (RG) improved effective potential
但是实际计算一般只能包含有限阶圈图的量子修正，比如一圈修正 即所谓 Coleman-Weinberg 势， 此时有效势将明显依赖重整化能标的选取，并影响微扰展开的有效性和精确度。那么一个重要的问题是如何选取重整化能标。
However, the practical calculations normally could only contain finite orders of loop-diagram quantum-corrections, for example, one-loop correction is the dubbed Coleman-Weinberg potential, and the corresponding effective potential would explicitly depend on the choice of renormalization scale and impact the effectiveness and precision of perturbative expansion. Then an important question is how to choose the renormalization scale.
首先我们可以退而求其次，要求重整化能标的某种选取函数 使得 为零，此时有效势由经过重整化群提升的经典势
Firstly, we could be conservative by requiring some function form for the renormalization scale so that is vanished, thus the corresponding effective potential is given by the RG-improved classical potential
Nevertheless, starting from the condition of a vanishing usually could not solve for an explicit function form of renormalization scale. Even such a explicit solution is obtained, it would be considerably complicated.
因此我们再次退而求其次，要求 虽然不为零但是其对数项尽可能的小，比如我们可以选取重整化群能标为 ，此时有效势是由经过重整化群提升的一圈修正有效势
Therefore, we can be even more conservative by requiring to be nonzero but as small as possible for its logarithmic part, for example, we could choose the renormalization scale as , and the corresponding effective potential is given by the RG-improved 1-loop-level effective potential
We could be even bolder by throwing away the whole 1-loop corrections and obtain the RG-improved tree-level effective potential