量子场论的方法和进展一直是理论物理的热点问题。 粒子物理标准模型在高能粒子对撞中得到了精确检验。为计算散射振幅，在微扰计算的同时，理论物理学家也发展了一系列解析的方法。如温伯格的软定理就解决了散射矩阵中一些很难处理的红外发散问题，而这些问题的由来可以归结为Null无穷远的渐进（BMS）对称性，即大（Large）规范变换。这些无穷维的BMS渐进对称性和温伯格的软定理彼此相关，互为联系。最近一个新的进展是发现它们与二维共形场论相关，这就意味着四维场论中隐含了一个二维共形场论，后者一个重要特征是其无穷维对称性及相应的可积性。这个二维共形场论由边界零动量光子（胶子）生成，生长在Null无穷远的二维边界球面上。它们与规范场在Null无穷远的渐进边界条件相关，对应于大（Large）规范变换。我们认为有必要进一步研究与之相关的二维共形场论与弦理论之间的关系，以及散射振幅中解析方法的应用。

Quantum field theory (QFT) is in the center of the theoretical physics, with its development coming along with inspiring new ideas perceiving the universe. One of the big successes of the QFT is the standard model in particle physics, which has survived the broad comparisons with the experimental data coming from the high energy colliders. Of course, the theoretical calculation of the scattering amplitudes depends on perturbative as well as analytical methods in QFT. As an example Weinberg's soft theorem has tamed the infrared divengencies due to soft photons or gravitons. While BCFW recursion relation is another example that the scattering amplitudes can be iterated with less external legs..It turns out that those soft photons are intimately related to the asymptotic (BMS) symmetries in the null infinity, which are generated by the large gauge transformations..Recent studies reveals that those infinite dimensional BMS asmptotic symmetries are in fact 2D conformal symmetries. And Weiberg's soft theorem is in fact the Ward identities related to the 2D Kac-Moody current algebra. It is plaussible that the associated 2D CFT is a reminiscence of the AdS/CFT correspondence, which can be stated roughly as that a string theory is dual to a gauge theory. Af course without protection from supersymmetry, this duality is not exact. However we speculate that in some sect suchstringy effect will emerge naturally. The objective of the present project is trying toformulate 2D CFT associated to 4D gauge theory in such a way that matches a string theory description.