论文标题
散射振幅的自然边界
Natural Boundaries for Scattering Amplitudes
论文作者
论文摘要
诸如极点和分支点之类的奇异性在研究散射幅度的分析特性中起着至关重要的作用，这些散射幅度为新的计算技术提供了信息。在本说明中，我们指出的是，散射幅度也可以具有另一种称为自然分析性界限的奇异性。它们创造了一个无法执行分析延续的障碍。更具体地说，我们使用Unitarity表明$ 2 \ 2 $的散射幅度在具有质量间隙的理论中可以在最轻的阈值切割的第二张纸上具有自然边界。在那里，无限数量的梯子型兰道奇异点在质量中心能量平面的真实轴上密集积聚。我们认为，自然边界是较高的理论中更高级散射幅度的通用特征。
Singularities, such as poles and branch points, play a crucial role in investigating the analytic properties of scattering amplitudes that inform new computational techniques. In this note, we point out that scattering amplitudes can also have another class of singularities called natural boundaries of analyticity. They create a barrier beyond which analytic continuation cannot be performed. More concretely, we use unitarity to show that $2 \to 2$ scattering amplitudes in theories with a mass gap can have a natural boundary on the second sheet of the lightest threshold cut. There, an infinite number of ladder-type Landau singularities densely accumulates on the real axis in the center-of-mass energy plane. We argue that natural boundaries are generic features of higher-multiplicity scattering amplitudes in gapped theories.
