arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1208.4847hep-phhep-th
收藏

规范理论放大器三、四环红外奇异性结构

Structure of Infrared Singularities of Gauge-Theory Amplitudes at Three and Four Loops

Valentin Ahrens, Matthias Neubert, Leonardo Vernazza

摘要:

在软共线有效理论中,由n喷注算符的反常维数可以导出无质量n部分子散射振幅的红外发散。直到三环阶,后者已经被证明具有非常简单的结构:它包含外部部分子之间的成对色偶极相互作用,由尖点反常维数和运动学不变量s_{ij}的对数控制,加上可能的涉及四个粒子的三环关联,这是由运动学不变量的共形交比的未知函数描述的。该函数受两粒子共线极限和高能极限中振幅的已知行为的约束。我们构造了一类满足这些约束的相对简单的函数。我们还扩展到四个循环的顺序分析,发现三个额外的四粒子相关性和一个单一的五粒子相关性出现,这又是由共形交比的功能。我们的研究结果表明,偶极猜想,其中规定,只有两个粒子的颜色偶极相关出现在反常的尺寸,可能需要推广。我们提出了一个较弱形式的猜想,指出在微扰论中,对偶极子公式的所有阶次的修正都是由共形交比的函数决定的,并且相对于偶极子项是O(1/N_c^2)抑制的。如果这个猜想成立,则意味着尖点反常维数在微扰论中服从Casimir标度。

英文摘要:

The infrared divergences of massless n-parton scattering amplitudes can be derived from the anomalous dimension of n-jet operators in soft-collinear effective theory. Up to three-loop order, the latter has been shown to have a very simple structure: it contains pairwise color-dipole interactions among the external partons, governed by the cusp anomalous dimension and a logarithm of the kinematic invariants s_{ij}, plus a possible three-loop correlation involving four particles, which is described by a yet unknown function of conformal cross ratios of kinematic invariants. This function is constrained by two-particle collinear limits and by the known behavior of amplitudes in the high-energy limit. We construct a class of relatively simple functions satisfying these constraints. We also extend the analysis to four-loop order, finding that three additional four-particle correlations and a single five-particle correlation appear, which again are governed by functions of conformal cross ratios. Our results suggest that the dipole conjecture, which states that only two-particle color-dipole correlations appear in the anomalous dimension, may need to be generalized. We present a weaker form of the conjecture, stating that to all orders in perturbation theory corrections to the dipole formula are governed by functions of conformal cross ratios, and are O(1/N_c^2) suppressed relative to the dipole term. If true, this conjecture implies that the cusp anomalous dimension obeys Casimir scaling to all orders in perturbation theory.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑