纯量胶球算子在Born水平上的解析结构
On the analytic structure of scalar glueball operators at Born level
摘要：
研究了描述纯量胶球的算子F2的两点函数的解析结构。所涉及的积分的计算是复杂的非解析结构的被积体，我们考虑到适当的确定切割产生的角积分和变形的轮廓相应的径向积分。所得分支点的位置符合Cutkosky的切割规则。作为输入，我们使用不同的非微扰朗道规范胶子传播与不同的分析性质，从晶格和功能的计算。它们都违反了正性，因而描述了在渐近物理空间中不存在的胶子。由此产生的胶球候选人的谱密度显示削减，但没有类光动量的极点，这可以归因于所采用的玻恩近似。
英文摘要：
We study the analytic structure of the two-point function of the operator F2 which is expected to describe a scalar glueball. The calculation of the involved integrals is complicated by nonanalytic structures in the integrands, which we take into account properly by identifying cuts generated by angular integrals and deforming the contours for the radial integration accordingly. The obtained locations of the branch points agree with Cutkosky's cut rules. As input we use different nonperturbative Landau gauge gluon propagators with different analytic properties as obtained from lattice and functional calculations. All of them violate positivity and describe thus gluons absent from the asymptotic physical space. The resulting spectral densities for the glueball candidate show a cut but no poles for lightlike momenta, which can be attributed to the employed Born approximation.
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